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-
- Linux Ethernet Bonding Driver HOWTO
-
- Latest update: 27 April 2011
-
-Initial release : Thomas Davis <tadavis at lbl.gov>
-Corrections, HA extensions : 2000/10/03-15 :
- - Willy Tarreau <willy at meta-x.org>
- - Constantine Gavrilov <const-g at xpert.com>
- - Chad N. Tindel <ctindel at ieee dot org>
- - Janice Girouard <girouard at us dot ibm dot com>
- - Jay Vosburgh <fubar at us dot ibm dot com>
-
-Reorganized and updated Feb 2005 by Jay Vosburgh
-Added Sysfs information: 2006/04/24
- - Mitch Williams <mitch.a.williams at intel.com>
-
-Introduction
-============
-
- The Linux bonding driver provides a method for aggregating
-multiple network interfaces into a single logical "bonded" interface.
-The behavior of the bonded interfaces depends upon the mode; generally
-speaking, modes provide either hot standby or load balancing services.
-Additionally, link integrity monitoring may be performed.
-
- The bonding driver originally came from Donald Becker's
-beowulf patches for kernel 2.0. It has changed quite a bit since, and
-the original tools from extreme-linux and beowulf sites will not work
-with this version of the driver.
-
- For new versions of the driver, updated userspace tools, and
-who to ask for help, please follow the links at the end of this file.
-
-Table of Contents
-=================
-
-1. Bonding Driver Installation
-
-2. Bonding Driver Options
-
-3. Configuring Bonding Devices
-3.1 Configuration with Sysconfig Support
-3.1.1 Using DHCP with Sysconfig
-3.1.2 Configuring Multiple Bonds with Sysconfig
-3.2 Configuration with Initscripts Support
-3.2.1 Using DHCP with Initscripts
-3.2.2 Configuring Multiple Bonds with Initscripts
-3.3 Configuring Bonding Manually with Ifenslave
-3.3.1 Configuring Multiple Bonds Manually
-3.4 Configuring Bonding Manually via Sysfs
-3.5 Configuration with Interfaces Support
-3.6 Overriding Configuration for Special Cases
-
-4. Querying Bonding Configuration
-4.1 Bonding Configuration
-4.2 Network Configuration
-
-5. Switch Configuration
-
-6. 802.1q VLAN Support
-
-7. Link Monitoring
-7.1 ARP Monitor Operation
-7.2 Configuring Multiple ARP Targets
-7.3 MII Monitor Operation
-
-8. Potential Trouble Sources
-8.1 Adventures in Routing
-8.2 Ethernet Device Renaming
-8.3 Painfully Slow Or No Failed Link Detection By Miimon
-
-9. SNMP agents
-
-10. Promiscuous mode
-
-11. Configuring Bonding for High Availability
-11.1 High Availability in a Single Switch Topology
-11.2 High Availability in a Multiple Switch Topology
-11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
-11.2.2 HA Link Monitoring for Multiple Switch Topology
-
-12. Configuring Bonding for Maximum Throughput
-12.1 Maximum Throughput in a Single Switch Topology
-12.1.1 MT Bonding Mode Selection for Single Switch Topology
-12.1.2 MT Link Monitoring for Single Switch Topology
-12.2 Maximum Throughput in a Multiple Switch Topology
-12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
-12.2.2 MT Link Monitoring for Multiple Switch Topology
-
-13. Switch Behavior Issues
-13.1 Link Establishment and Failover Delays
-13.2 Duplicated Incoming Packets
-
-14. Hardware Specific Considerations
-14.1 IBM BladeCenter
-
-15. Frequently Asked Questions
-
-16. Resources and Links
-
-
-1. Bonding Driver Installation
-==============================
-
- Most popular distro kernels ship with the bonding driver
-already available as a module and the ifenslave user level control
-program installed and ready for use. If your distro does not, or you
-have need to compile bonding from source (e.g., configuring and
-installing a mainline kernel from kernel.org), you'll need to perform
-the following steps:
-
-1.1 Configure and build the kernel with bonding
------------------------------------------------
-
- The current version of the bonding driver is available in the
-drivers/net/bonding subdirectory of the most recent kernel source
-(which is available on http://kernel.org). Most users "rolling their
-own" will want to use the most recent kernel from kernel.org.
-
- Configure kernel with "make menuconfig" (or "make xconfig" or
-"make config"), then select "Bonding driver support" in the "Network
-device support" section. It is recommended that you configure the
-driver as module since it is currently the only way to pass parameters
-to the driver or configure more than one bonding device.
-
- Build and install the new kernel and modules, then continue
-below to install ifenslave.
-
-1.2 Install ifenslave Control Utility
--------------------------------------
-
- The ifenslave user level control program is included in the
-kernel source tree, in the file Documentation/networking/ifenslave.c.
-It is generally recommended that you use the ifenslave that
-corresponds to the kernel that you are using (either from the same
-source tree or supplied with the distro), however, ifenslave
-executables from older kernels should function (but features newer
-than the ifenslave release are not supported). Running an ifenslave
-that is newer than the kernel is not supported, and may or may not
-work.
-
- To install ifenslave, do the following:
-
-# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave
-# cp ifenslave /sbin/ifenslave
-
- If your kernel source is not in "/usr/src/linux," then replace
-"/usr/src/linux/include" in the above with the location of your kernel
-source include directory.
-
- You may wish to back up any existing /sbin/ifenslave, or, for
-testing or informal use, tag the ifenslave to the kernel version
-(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10).
-
-IMPORTANT NOTE:
-
- If you omit the "-I" or specify an incorrect directory, you
-may end up with an ifenslave that is incompatible with the kernel
-you're trying to build it for. Some distros (e.g., Red Hat from 7.1
-onwards) do not have /usr/include/linux symbolically linked to the
-default kernel source include directory.
-
-SECOND IMPORTANT NOTE:
- If you plan to configure bonding using sysfs or using the
-/etc/network/interfaces file, you do not need to use ifenslave.
-
-2. Bonding Driver Options
-=========================
-
- Options for the bonding driver are supplied as parameters to the
-bonding module at load time, or are specified via sysfs.
-
- Module options may be given as command line arguments to the
-insmod or modprobe command, but are usually specified in either the
-/etc/modrobe.d/*.conf configuration files, or in a distro-specific
-configuration file (some of which are detailed in the next section).
-
- Details on bonding support for sysfs is provided in the
-"Configuring Bonding Manually via Sysfs" section, below.
-
- The available bonding driver parameters are listed below. If a
-parameter is not specified the default value is used. When initially
-configuring a bond, it is recommended "tail -f /var/log/messages" be
-run in a separate window to watch for bonding driver error messages.
-
- It is critical that either the miimon or arp_interval and
-arp_ip_target parameters be specified, otherwise serious network
-degradation will occur during link failures. Very few devices do not
-support at least miimon, so there is really no reason not to use it.
-
- Options with textual values will accept either the text name
-or, for backwards compatibility, the option value. E.g.,
-"mode=802.3ad" and "mode=4" set the same mode.
-
- The parameters are as follows:
-
-active_slave
-
- Specifies the new active slave for modes that support it
- (active-backup, balance-alb and balance-tlb). Possible values
- are the name of any currently enslaved interface, or an empty
- string. If a name is given, the slave and its link must be up in order
- to be selected as the new active slave. If an empty string is
- specified, the current active slave is cleared, and a new active
- slave is selected automatically.
-
- Note that this is only available through the sysfs interface. No module
- parameter by this name exists.
-
- The normal value of this option is the name of the currently
- active slave, or the empty string if there is no active slave or
- the current mode does not use an active slave.
-
-ad_select
-
- Specifies the 802.3ad aggregation selection logic to use. The
- possible values and their effects are:
-
- stable or 0
-
- The active aggregator is chosen by largest aggregate
- bandwidth.
-
- Reselection of the active aggregator occurs only when all
- slaves of the active aggregator are down or the active
- aggregator has no slaves.
-
- This is the default value.
-
- bandwidth or 1
-
- The active aggregator is chosen by largest aggregate
- bandwidth. Reselection occurs if:
-
- - A slave is added to or removed from the bond
-
- - Any slave's link state changes
-
- - Any slave's 802.3ad association state changes
-
- - The bond's administrative state changes to up
-
- count or 2
-
- The active aggregator is chosen by the largest number of
- ports (slaves). Reselection occurs as described under the
- "bandwidth" setting, above.
-
- The bandwidth and count selection policies permit failover of
- 802.3ad aggregations when partial failure of the active aggregator
- occurs. This keeps the aggregator with the highest availability
- (either in bandwidth or in number of ports) active at all times.
-
- This option was added in bonding version 3.4.0.
-
-all_slaves_active
-
- Specifies that duplicate frames (received on inactive ports) should be
- dropped (0) or delivered (1).
-
- Normally, bonding will drop duplicate frames (received on inactive
- ports), which is desirable for most users. But there are some times
- it is nice to allow duplicate frames to be delivered.
-
- The default value is 0 (drop duplicate frames received on inactive
- ports).
-
-arp_interval
-
- Specifies the ARP link monitoring frequency in milliseconds.
-
- The ARP monitor works by periodically checking the slave
- devices to determine whether they have sent or received
- traffic recently (the precise criteria depends upon the
- bonding mode, and the state of the slave). Regular traffic is
- generated via ARP probes issued for the addresses specified by
- the arp_ip_target option.
-
- This behavior can be modified by the arp_validate option,
- below.
-
- If ARP monitoring is used in an etherchannel compatible mode
- (modes 0 and 2), the switch should be configured in a mode
- that evenly distributes packets across all links. If the
- switch is configured to distribute the packets in an XOR
- fashion, all replies from the ARP targets will be received on
- the same link which could cause the other team members to
- fail. ARP monitoring should not be used in conjunction with
- miimon. A value of 0 disables ARP monitoring. The default
- value is 0.
-
-arp_ip_target
-
- Specifies the IP addresses to use as ARP monitoring peers when
- arp_interval is > 0. These are the targets of the ARP request
- sent to determine the health of the link to the targets.
- Specify these values in ddd.ddd.ddd.ddd format. Multiple IP
- addresses must be separated by a comma. At least one IP
- address must be given for ARP monitoring to function. The
- maximum number of targets that can be specified is 16. The
- default value is no IP addresses.
-
-arp_validate
-
- Specifies whether or not ARP probes and replies should be
- validated in the active-backup mode. This causes the ARP
- monitor to examine the incoming ARP requests and replies, and
- only consider a slave to be up if it is receiving the
- appropriate ARP traffic.
-
- Possible values are:
-
- none or 0
-
- No validation is performed. This is the default.
-
- active or 1
-
- Validation is performed only for the active slave.
-
- backup or 2
-
- Validation is performed only for backup slaves.
-
- all or 3
-
- Validation is performed for all slaves.
-
- For the active slave, the validation checks ARP replies to
- confirm that they were generated by an arp_ip_target. Since
- backup slaves do not typically receive these replies, the
- validation performed for backup slaves is on the ARP request
- sent out via the active slave. It is possible that some
- switch or network configurations may result in situations
- wherein the backup slaves do not receive the ARP requests; in
- such a situation, validation of backup slaves must be
- disabled.
-
- This option is useful in network configurations in which
- multiple bonding hosts are concurrently issuing ARPs to one or
- more targets beyond a common switch. Should the link between
- the switch and target fail (but not the switch itself), the
- probe traffic generated by the multiple bonding instances will
- fool the standard ARP monitor into considering the links as
- still up. Use of the arp_validate option can resolve this, as
- the ARP monitor will only consider ARP requests and replies
- associated with its own instance of bonding.
-
- This option was added in bonding version 3.1.0.
-
-downdelay
-
- Specifies the time, in milliseconds, to wait before disabling
- a slave after a link failure has been detected. This option
- is only valid for the miimon link monitor. The downdelay
- value should be a multiple of the miimon value; if not, it
- will be rounded down to the nearest multiple. The default
- value is 0.
-
-fail_over_mac
-
- Specifies whether active-backup mode should set all slaves to
- the same MAC address at enslavement (the traditional
- behavior), or, when enabled, perform special handling of the
- bond's MAC address in accordance with the selected policy.
-
- Possible values are:
-
- none or 0
-
- This setting disables fail_over_mac, and causes
- bonding to set all slaves of an active-backup bond to
- the same MAC address at enslavement time. This is the
- default.
-
- active or 1
-
- The "active" fail_over_mac policy indicates that the
- MAC address of the bond should always be the MAC
- address of the currently active slave. The MAC
- address of the slaves is not changed; instead, the MAC
- address of the bond changes during a failover.
-
- This policy is useful for devices that cannot ever
- alter their MAC address, or for devices that refuse
- incoming broadcasts with their own source MAC (which
- interferes with the ARP monitor).
-
- The down side of this policy is that every device on
- the network must be updated via gratuitous ARP,
- vs. just updating a switch or set of switches (which
- often takes place for any traffic, not just ARP
- traffic, if the switch snoops incoming traffic to
- update its tables) for the traditional method. If the
- gratuitous ARP is lost, communication may be
- disrupted.
-
- When this policy is used in conjunction with the mii
- monitor, devices which assert link up prior to being
- able to actually transmit and receive are particularly
- susceptible to loss of the gratuitous ARP, and an
- appropriate updelay setting may be required.
-
- follow or 2
-
- The "follow" fail_over_mac policy causes the MAC
- address of the bond to be selected normally (normally
- the MAC address of the first slave added to the bond).
- However, the second and subsequent slaves are not set
- to this MAC address while they are in a backup role; a
- slave is programmed with the bond's MAC address at
- failover time (and the formerly active slave receives
- the newly active slave's MAC address).
-
- This policy is useful for multiport devices that
- either become confused or incur a performance penalty
- when multiple ports are programmed with the same MAC
- address.
-
-
- The default policy is none, unless the first slave cannot
- change its MAC address, in which case the active policy is
- selected by default.
-
- This option may be modified via sysfs only when no slaves are
- present in the bond.
-
- This option was added in bonding version 3.2.0. The "follow"
- policy was added in bonding version 3.3.0.
-
-lacp_rate
-
- Option specifying the rate in which we'll ask our link partner
- to transmit LACPDU packets in 802.3ad mode. Possible values
- are:
-
- slow or 0
- Request partner to transmit LACPDUs every 30 seconds
-
- fast or 1
- Request partner to transmit LACPDUs every 1 second
-
- The default is slow.
-
-max_bonds
-
- Specifies the number of bonding devices to create for this
- instance of the bonding driver. E.g., if max_bonds is 3, and
- the bonding driver is not already loaded, then bond0, bond1
- and bond2 will be created. The default value is 1. Specifying
- a value of 0 will load bonding, but will not create any devices.
-
-miimon
-
- Specifies the MII link monitoring frequency in milliseconds.
- This determines how often the link state of each slave is
- inspected for link failures. A value of zero disables MII
- link monitoring. A value of 100 is a good starting point.
- The use_carrier option, below, affects how the link state is
- determined. See the High Availability section for additional
- information. The default value is 0.
-
-min_links
-
- Specifies the minimum number of links that must be active before
- asserting carrier. It is similar to the Cisco EtherChannel min-links
- feature. This allows setting the minimum number of member ports that
- must be up (link-up state) before marking the bond device as up
- (carrier on). This is useful for situations where higher level services
- such as clustering want to ensure a minimum number of low bandwidth
- links are active before switchover. This option only affect 802.3ad
- mode.
-
- The default value is 0. This will cause carrier to be asserted (for
- 802.3ad mode) whenever there is an active aggregator, regardless of the
- number of available links in that aggregator. Note that, because an
- aggregator cannot be active without at least one available link,
- setting this option to 0 or to 1 has the exact same effect.
-
-mode
-
- Specifies one of the bonding policies. The default is
- balance-rr (round robin). Possible values are:
-
- balance-rr or 0
-
- Round-robin policy: Transmit packets in sequential
- order from the first available slave through the
- last. This mode provides load balancing and fault
- tolerance.
-
- active-backup or 1
-
- Active-backup policy: Only one slave in the bond is
- active. A different slave becomes active if, and only
- if, the active slave fails. The bond's MAC address is
- externally visible on only one port (network adapter)
- to avoid confusing the switch.
-
- In bonding version 2.6.2 or later, when a failover
- occurs in active-backup mode, bonding will issue one
- or more gratuitous ARPs on the newly active slave.
- One gratuitous ARP is issued for the bonding master
- interface and each VLAN interfaces configured above
- it, provided that the interface has at least one IP
- address configured. Gratuitous ARPs issued for VLAN
- interfaces are tagged with the appropriate VLAN id.
-
- This mode provides fault tolerance. The primary
- option, documented below, affects the behavior of this
- mode.
-
- balance-xor or 2
-
- XOR policy: Transmit based on the selected transmit
- hash policy. The default policy is a simple [(source
- MAC address XOR'd with destination MAC address) modulo
- slave count]. Alternate transmit policies may be
- selected via the xmit_hash_policy option, described
- below.
-
- This mode provides load balancing and fault tolerance.
-
- broadcast or 3
-
- Broadcast policy: transmits everything on all slave
- interfaces. This mode provides fault tolerance.
-
- 802.3ad or 4
-
- IEEE 802.3ad Dynamic link aggregation. Creates
- aggregation groups that share the same speed and
- duplex settings. Utilizes all slaves in the active
- aggregator according to the 802.3ad specification.
-
- Slave selection for outgoing traffic is done according
- to the transmit hash policy, which may be changed from
- the default simple XOR policy via the xmit_hash_policy
- option, documented below. Note that not all transmit
- policies may be 802.3ad compliant, particularly in
- regards to the packet mis-ordering requirements of
- section 43.2.4 of the 802.3ad standard. Differing
- peer implementations will have varying tolerances for
- noncompliance.
-
- Prerequisites:
-
- 1. Ethtool support in the base drivers for retrieving
- the speed and duplex of each slave.
-
- 2. A switch that supports IEEE 802.3ad Dynamic link
- aggregation.
-
- Most switches will require some type of configuration
- to enable 802.3ad mode.
-
- balance-tlb or 5
-
- Adaptive transmit load balancing: channel bonding that
- does not require any special switch support. The
- outgoing traffic is distributed according to the
- current load (computed relative to the speed) on each
- slave. Incoming traffic is received by the current
- slave. If the receiving slave fails, another slave
- takes over the MAC address of the failed receiving
- slave.
-
- Prerequisite:
-
- Ethtool support in the base drivers for retrieving the
- speed of each slave.
-
- balance-alb or 6
-
- Adaptive load balancing: includes balance-tlb plus
- receive load balancing (rlb) for IPV4 traffic, and
- does not require any special switch support. The
- receive load balancing is achieved by ARP negotiation.
- The bonding driver intercepts the ARP Replies sent by
- the local system on their way out and overwrites the
- source hardware address with the unique hardware
- address of one of the slaves in the bond such that
- different peers use different hardware addresses for
- the server.
-
- Receive traffic from connections created by the server
- is also balanced. When the local system sends an ARP
- Request the bonding driver copies and saves the peer's
- IP information from the ARP packet. When the ARP
- Reply arrives from the peer, its hardware address is
- retrieved and the bonding driver initiates an ARP
- reply to this peer assigning it to one of the slaves
- in the bond. A problematic outcome of using ARP
- negotiation for balancing is that each time that an
- ARP request is broadcast it uses the hardware address
- of the bond. Hence, peers learn the hardware address
- of the bond and the balancing of receive traffic
- collapses to the current slave. This is handled by
- sending updates (ARP Replies) to all the peers with
- their individually assigned hardware address such that
- the traffic is redistributed. Receive traffic is also
- redistributed when a new slave is added to the bond
- and when an inactive slave is re-activated. The
- receive load is distributed sequentially (round robin)
- among the group of highest speed slaves in the bond.
-
- When a link is reconnected or a new slave joins the
- bond the receive traffic is redistributed among all
- active slaves in the bond by initiating ARP Replies
- with the selected MAC address to each of the
- clients. The updelay parameter (detailed below) must
- be set to a value equal or greater than the switch's
- forwarding delay so that the ARP Replies sent to the
- peers will not be blocked by the switch.
-
- Prerequisites:
-
- 1. Ethtool support in the base drivers for retrieving
- the speed of each slave.
-
- 2. Base driver support for setting the hardware
- address of a device while it is open. This is
- required so that there will always be one slave in the
- team using the bond hardware address (the
- curr_active_slave) while having a unique hardware
- address for each slave in the bond. If the
- curr_active_slave fails its hardware address is
- swapped with the new curr_active_slave that was
- chosen.
-
-num_grat_arp
-num_unsol_na
-
- Specify the number of peer notifications (gratuitous ARPs and
- unsolicited IPv6 Neighbor Advertisements) to be issued after a
- failover event. As soon as the link is up on the new slave
- (possibly immediately) a peer notification is sent on the
- bonding device and each VLAN sub-device. This is repeated at
- each link monitor interval (arp_interval or miimon, whichever
- is active) if the number is greater than 1.
-
- The valid range is 0 - 255; the default value is 1. These options
- affect only the active-backup mode. These options were added for
- bonding versions 3.3.0 and 3.4.0 respectively.
-
- From Linux 3.0 and bonding version 3.7.1, these notifications
- are generated by the ipv4 and ipv6 code and the numbers of
- repetitions cannot be set independently.
-
-primary
-
- A string (eth0, eth2, etc) specifying which slave is the
- primary device. The specified device will always be the
- active slave while it is available. Only when the primary is
- off-line will alternate devices be used. This is useful when
- one slave is preferred over another, e.g., when one slave has
- higher throughput than another.
-
- The primary option is only valid for active-backup mode.
-
-primary_reselect
-
- Specifies the reselection policy for the primary slave. This
- affects how the primary slave is chosen to become the active slave
- when failure of the active slave or recovery of the primary slave
- occurs. This option is designed to prevent flip-flopping between
- the primary slave and other slaves. Possible values are:
-
- always or 0 (default)
-
- The primary slave becomes the active slave whenever it
- comes back up.
-
- better or 1
-
- The primary slave becomes the active slave when it comes
- back up, if the speed and duplex of the primary slave is
- better than the speed and duplex of the current active
- slave.
-
- failure or 2
-
- The primary slave becomes the active slave only if the
- current active slave fails and the primary slave is up.
-
- The primary_reselect setting is ignored in two cases:
-
- If no slaves are active, the first slave to recover is
- made the active slave.
-
- When initially enslaved, the primary slave is always made
- the active slave.
-
- Changing the primary_reselect policy via sysfs will cause an
- immediate selection of the best active slave according to the new
- policy. This may or may not result in a change of the active
- slave, depending upon the circumstances.
-
- This option was added for bonding version 3.6.0.
-
-updelay
-
- Specifies the time, in milliseconds, to wait before enabling a
- slave after a link recovery has been detected. This option is
- only valid for the miimon link monitor. The updelay value
- should be a multiple of the miimon value; if not, it will be
- rounded down to the nearest multiple. The default value is 0.
-
-use_carrier
-
- Specifies whether or not miimon should use MII or ETHTOOL
- ioctls vs. netif_carrier_ok() to determine the link
- status. The MII or ETHTOOL ioctls are less efficient and
- utilize a deprecated calling sequence within the kernel. The
- netif_carrier_ok() relies on the device driver to maintain its
- state with netif_carrier_on/off; at this writing, most, but
- not all, device drivers support this facility.
-
- If bonding insists that the link is up when it should not be,
- it may be that your network device driver does not support
- netif_carrier_on/off. The default state for netif_carrier is
- "carrier on," so if a driver does not support netif_carrier,
- it will appear as if the link is always up. In this case,
- setting use_carrier to 0 will cause bonding to revert to the
- MII / ETHTOOL ioctl method to determine the link state.
-
- A value of 1 enables the use of netif_carrier_ok(), a value of
- 0 will use the deprecated MII / ETHTOOL ioctls. The default
- value is 1.
-
-xmit_hash_policy
-
- Selects the transmit hash policy to use for slave selection in
- balance-xor and 802.3ad modes. Possible values are:
-
- layer2
-
- Uses XOR of hardware MAC addresses to generate the
- hash. The formula is
-
- (source MAC XOR destination MAC) modulo slave count
-
- This algorithm will place all traffic to a particular
- network peer on the same slave.
-
- This algorithm is 802.3ad compliant.
-
- layer2+3
-
- This policy uses a combination of layer2 and layer3
- protocol information to generate the hash.
-
- Uses XOR of hardware MAC addresses and IP addresses to
- generate the hash. The formula is
-
- (((source IP XOR dest IP) AND 0xffff) XOR
- ( source MAC XOR destination MAC ))
- modulo slave count
-
- This algorithm will place all traffic to a particular
- network peer on the same slave. For non-IP traffic,
- the formula is the same as for the layer2 transmit
- hash policy.
-
- This policy is intended to provide a more balanced
- distribution of traffic than layer2 alone, especially
- in environments where a layer3 gateway device is
- required to reach most destinations.
-
- This algorithm is 802.3ad compliant.
-
- layer3+4
-
- This policy uses upper layer protocol information,
- when available, to generate the hash. This allows for
- traffic to a particular network peer to span multiple
- slaves, although a single connection will not span
- multiple slaves.
-
- The formula for unfragmented TCP and UDP packets is
-
- ((source port XOR dest port) XOR
- ((source IP XOR dest IP) AND 0xffff)
- modulo slave count
-
- For fragmented TCP or UDP packets and all other IP
- protocol traffic, the source and destination port
- information is omitted. For non-IP traffic, the
- formula is the same as for the layer2 transmit hash
- policy.
-
- This policy is intended to mimic the behavior of
- certain switches, notably Cisco switches with PFC2 as
- well as some Foundry and IBM products.
-
- This algorithm is not fully 802.3ad compliant. A
- single TCP or UDP conversation containing both
- fragmented and unfragmented packets will see packets
- striped across two interfaces. This may result in out
- of order delivery. Most traffic types will not meet
- this criteria, as TCP rarely fragments traffic, and
- most UDP traffic is not involved in extended
- conversations. Other implementations of 802.3ad may
- or may not tolerate this noncompliance.
-
- The default value is layer2. This option was added in bonding
- version 2.6.3. In earlier versions of bonding, this parameter
- does not exist, and the layer2 policy is the only policy. The
- layer2+3 value was added for bonding version 3.2.2.
-
-resend_igmp
-
- Specifies the number of IGMP membership reports to be issued after
- a failover event. One membership report is issued immediately after
- the failover, subsequent packets are sent in each 200ms interval.
-
- The valid range is 0 - 255; the default value is 1. A value of 0
- prevents the IGMP membership report from being issued in response
- to the failover event.
-
- This option is useful for bonding modes balance-rr (0), active-backup
- (1), balance-tlb (5) and balance-alb (6), in which a failover can
- switch the IGMP traffic from one slave to another. Therefore a fresh
- IGMP report must be issued to cause the switch to forward the incoming
- IGMP traffic over the newly selected slave.
-
- This option was added for bonding version 3.7.0.
-
-3. Configuring Bonding Devices
-==============================
-
- You can configure bonding using either your distro's network
-initialization scripts, or manually using either ifenslave or the
-sysfs interface. Distros generally use one of three packages for the
-network initialization scripts: initscripts, sysconfig or interfaces.
-Recent versions of these packages have support for bonding, while older
-versions do not.
-
- We will first describe the options for configuring bonding for
-distros using versions of initscripts, sysconfig and interfaces with full
-or partial support for bonding, then provide information on enabling
-bonding without support from the network initialization scripts (i.e.,
-older versions of initscripts or sysconfig).
-
- If you're unsure whether your distro uses sysconfig,
-initscripts or interfaces, or don't know if it's new enough, have no fear.
-Determining this is fairly straightforward.
-
- First, look for a file called interfaces in /etc/network directory.
-If this file is present in your system, then your system use interfaces. See
-Configuration with Interfaces Support.
-
- Else, issue the command:
-
-$ rpm -qf /sbin/ifup
-
- It will respond with a line of text starting with either
-"initscripts" or "sysconfig," followed by some numbers. This is the
-package that provides your network initialization scripts.
-
- Next, to determine if your installation supports bonding,
-issue the command:
-
-$ grep ifenslave /sbin/ifup
-
- If this returns any matches, then your initscripts or
-sysconfig has support for bonding.
-
-3.1 Configuration with Sysconfig Support
-----------------------------------------
-
- This section applies to distros using a version of sysconfig
-with bonding support, for example, SuSE Linux Enterprise Server 9.
-
- SuSE SLES 9's networking configuration system does support
-bonding, however, at this writing, the YaST system configuration
-front end does not provide any means to work with bonding devices.
-Bonding devices can be managed by hand, however, as follows.
-
- First, if they have not already been configured, configure the
-slave devices. On SLES 9, this is most easily done by running the
-yast2 sysconfig configuration utility. The goal is for to create an
-ifcfg-id file for each slave device. The simplest way to accomplish
-this is to configure the devices for DHCP (this is only to get the
-file ifcfg-id file created; see below for some issues with DHCP). The
-name of the configuration file for each device will be of the form:
-
-ifcfg-id-xx:xx:xx:xx:xx:xx
-
- Where the "xx" portion will be replaced with the digits from
-the device's permanent MAC address.
-
- Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
-created, it is necessary to edit the configuration files for the slave
-devices (the MAC addresses correspond to those of the slave devices).
-Before editing, the file will contain multiple lines, and will look
-something like this:
-
-BOOTPROTO='dhcp'
-STARTMODE='on'
-USERCTL='no'
-UNIQUE='XNzu.WeZGOGF+4wE'
-_nm_name='bus-pci-0001:61:01.0'
-
- Change the BOOTPROTO and STARTMODE lines to the following:
-
-BOOTPROTO='none'
-STARTMODE='off'
-
- Do not alter the UNIQUE or _nm_name lines. Remove any other
-lines (USERCTL, etc).
-
- Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
-it's time to create the configuration file for the bonding device
-itself. This file is named ifcfg-bondX, where X is the number of the
-bonding device to create, starting at 0. The first such file is
-ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
-network configuration system will correctly start multiple instances
-of bonding.
-
- The contents of the ifcfg-bondX file is as follows:
-
-BOOTPROTO="static"
-BROADCAST="10.0.2.255"
-IPADDR="10.0.2.10"
-NETMASK="255.255.0.0"
-NETWORK="10.0.2.0"
-REMOTE_IPADDR=""
-STARTMODE="onboot"
-BONDING_MASTER="yes"
-BONDING_MODULE_OPTS="mode=active-backup miimon=100"
-BONDING_SLAVE0="eth0"
-BONDING_SLAVE1="bus-pci-0000:06:08.1"
-
- Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
-values with the appropriate values for your network.
-
- The STARTMODE specifies when the device is brought online.
-The possible values are:
-
- onboot: The device is started at boot time. If you're not
- sure, this is probably what you want.
-
- manual: The device is started only when ifup is called
- manually. Bonding devices may be configured this
- way if you do not wish them to start automatically
- at boot for some reason.
-
- hotplug: The device is started by a hotplug event. This is not
- a valid choice for a bonding device.
-
- off or ignore: The device configuration is ignored.
-
- The line BONDING_MASTER='yes' indicates that the device is a
-bonding master device. The only useful value is "yes."
-
- The contents of BONDING_MODULE_OPTS are supplied to the
-instance of the bonding module for this device. Specify the options
-for the bonding mode, link monitoring, and so on here. Do not include
-the max_bonds bonding parameter; this will confuse the configuration
-system if you have multiple bonding devices.
-
- Finally, supply one BONDING_SLAVEn="slave device" for each
-slave. where "n" is an increasing value, one for each slave. The
-"slave device" is either an interface name, e.g., "eth0", or a device
-specifier for the network device. The interface name is easier to
-find, but the ethN names are subject to change at boot time if, e.g.,
-a device early in the sequence has failed. The device specifiers
-(bus-pci-0000:06:08.1 in the example above) specify the physical
-network device, and will not change unless the device's bus location
-changes (for example, it is moved from one PCI slot to another). The
-example above uses one of each type for demonstration purposes; most
-configurations will choose one or the other for all slave devices.
-
- When all configuration files have been modified or created,
-networking must be restarted for the configuration changes to take
-effect. This can be accomplished via the following:
-
-# /etc/init.d/network restart
-
- Note that the network control script (/sbin/ifdown) will
-remove the bonding module as part of the network shutdown processing,
-so it is not necessary to remove the module by hand if, e.g., the
-module parameters have changed.
-
- Also, at this writing, YaST/YaST2 will not manage bonding
-devices (they do not show bonding interfaces on its list of network
-devices). It is necessary to edit the configuration file by hand to
-change the bonding configuration.
-
- Additional general options and details of the ifcfg file
-format can be found in an example ifcfg template file:
-
-/etc/sysconfig/network/ifcfg.template
-
- Note that the template does not document the various BONDING_
-settings described above, but does describe many of the other options.
-
-3.1.1 Using DHCP with Sysconfig
--------------------------------
-
- Under sysconfig, configuring a device with BOOTPROTO='dhcp'
-will cause it to query DHCP for its IP address information. At this
-writing, this does not function for bonding devices; the scripts
-attempt to obtain the device address from DHCP prior to adding any of
-the slave devices. Without active slaves, the DHCP requests are not
-sent to the network.
-
-3.1.2 Configuring Multiple Bonds with Sysconfig
------------------------------------------------
-
- The sysconfig network initialization system is capable of
-handling multiple bonding devices. All that is necessary is for each
-bonding instance to have an appropriately configured ifcfg-bondX file
-(as described above). Do not specify the "max_bonds" parameter to any
-instance of bonding, as this will confuse sysconfig. If you require
-multiple bonding devices with identical parameters, create multiple
-ifcfg-bondX files.
-
- Because the sysconfig scripts supply the bonding module
-options in the ifcfg-bondX file, it is not necessary to add them to
-the system /etc/modules.d/*.conf configuration files.
-
-3.2 Configuration with Initscripts Support
-------------------------------------------
-
- This section applies to distros using a recent version of
-initscripts with bonding support, for example, Red Hat Enterprise Linux
-version 3 or later, Fedora, etc. On these systems, the network
-initialization scripts have knowledge of bonding, and can be configured to
-control bonding devices. Note that older versions of the initscripts
-package have lower levels of support for bonding; this will be noted where
-applicable.
-
- These distros will not automatically load the network adapter
-driver unless the ethX device is configured with an IP address.
-Because of this constraint, users must manually configure a
-network-script file for all physical adapters that will be members of
-a bondX link. Network script files are located in the directory:
-
-/etc/sysconfig/network-scripts
-
- The file name must be prefixed with "ifcfg-eth" and suffixed
-with the adapter's physical adapter number. For example, the script
-for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
-Place the following text in the file:
-
-DEVICE=eth0
-USERCTL=no
-ONBOOT=yes
-MASTER=bond0
-SLAVE=yes
-BOOTPROTO=none
-
- The DEVICE= line will be different for every ethX device and
-must correspond with the name of the file, i.e., ifcfg-eth1 must have
-a device line of DEVICE=eth1. The setting of the MASTER= line will
-also depend on the final bonding interface name chosen for your bond.
-As with other network devices, these typically start at 0, and go up
-one for each device, i.e., the first bonding instance is bond0, the
-second is bond1, and so on.
-
- Next, create a bond network script. The file name for this
-script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
-the number of the bond. For bond0 the file is named "ifcfg-bond0",
-for bond1 it is named "ifcfg-bond1", and so on. Within that file,
-place the following text:
-
-DEVICE=bond0
-IPADDR=192.168.1.1
-NETMASK=255.255.255.0
-NETWORK=192.168.1.0
-BROADCAST=192.168.1.255
-ONBOOT=yes
-BOOTPROTO=none
-USERCTL=no
-
- Be sure to change the networking specific lines (IPADDR,
-NETMASK, NETWORK and BROADCAST) to match your network configuration.
-
- For later versions of initscripts, such as that found with Fedora
-7 (or later) and Red Hat Enterprise Linux version 5 (or later), it is possible,
-and, indeed, preferable, to specify the bonding options in the ifcfg-bond0
-file, e.g. a line of the format:
-
-BONDING_OPTS="mode=active-backup arp_interval=60 arp_ip_target=192.168.1.254"
-
- will configure the bond with the specified options. The options
-specified in BONDING_OPTS are identical to the bonding module parameters
-except for the arp_ip_target field when using versions of initscripts older
-than and 8.57 (Fedora 8) and 8.45.19 (Red Hat Enterprise Linux 5.2). When
-using older versions each target should be included as a separate option and
-should be preceded by a '+' to indicate it should be added to the list of
-queried targets, e.g.,
-
- arp_ip_target=+192.168.1.1 arp_ip_target=+192.168.1.2
-
- is the proper syntax to specify multiple targets. When specifying
-options via BONDING_OPTS, it is not necessary to edit /etc/modprobe.d/*.conf.
-
- For even older versions of initscripts that do not support
-BONDING_OPTS, it is necessary to edit /etc/modprobe.d/*.conf, depending upon
-your distro) to load the bonding module with your desired options when the
-bond0 interface is brought up. The following lines in /etc/modprobe.d/*.conf
-will load the bonding module, and select its options:
-
-alias bond0 bonding
-options bond0 mode=balance-alb miimon=100
-
- Replace the sample parameters with the appropriate set of
-options for your configuration.
-
- Finally run "/etc/rc.d/init.d/network restart" as root. This
-will restart the networking subsystem and your bond link should be now
-up and running.
-
-3.2.1 Using DHCP with Initscripts
----------------------------------
-
- Recent versions of initscripts (the versions supplied with Fedora
-Core 3 and Red Hat Enterprise Linux 4, or later versions, are reported to
-work) have support for assigning IP information to bonding devices via
-DHCP.
-
- To configure bonding for DHCP, configure it as described
-above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
-and add a line consisting of "TYPE=Bonding". Note that the TYPE value
-is case sensitive.
-
-3.2.2 Configuring Multiple Bonds with Initscripts
--------------------------------------------------
-
- Initscripts packages that are included with Fedora 7 and Red Hat
-Enterprise Linux 5 support multiple bonding interfaces by simply
-specifying the appropriate BONDING_OPTS= in ifcfg-bondX where X is the
-number of the bond. This support requires sysfs support in the kernel,
-and a bonding driver of version 3.0.0 or later. Other configurations may
-not support this method for specifying multiple bonding interfaces; for
-those instances, see the "Configuring Multiple Bonds Manually" section,
-below.
-
-3.3 Configuring Bonding Manually with Ifenslave
------------------------------------------------
-
- This section applies to distros whose network initialization
-scripts (the sysconfig or initscripts package) do not have specific
-knowledge of bonding. One such distro is SuSE Linux Enterprise Server
-version 8.
-
- The general method for these systems is to place the bonding
-module parameters into a config file in /etc/modprobe.d/ (as
-appropriate for the installed distro), then add modprobe and/or
-ifenslave commands to the system's global init script. The name of
-the global init script differs; for sysconfig, it is
-/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
-
- For example, if you wanted to make a simple bond of two e100
-devices (presumed to be eth0 and eth1), and have it persist across
-reboots, edit the appropriate file (/etc/init.d/boot.local or
-/etc/rc.d/rc.local), and add the following:
-
-modprobe bonding mode=balance-alb miimon=100
-modprobe e100
-ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
-ifenslave bond0 eth0
-ifenslave bond0 eth1
-
- Replace the example bonding module parameters and bond0
-network configuration (IP address, netmask, etc) with the appropriate
-values for your configuration.
-
- Unfortunately, this method will not provide support for the
-ifup and ifdown scripts on the bond devices. To reload the bonding
-configuration, it is necessary to run the initialization script, e.g.,
-
-# /etc/init.d/boot.local
-
- or
-
-# /etc/rc.d/rc.local
-
- It may be desirable in such a case to create a separate script
-which only initializes the bonding configuration, then call that
-separate script from within boot.local. This allows for bonding to be
-enabled without re-running the entire global init script.
-
- To shut down the bonding devices, it is necessary to first
-mark the bonding device itself as being down, then remove the
-appropriate device driver modules. For our example above, you can do
-the following:
-
-# ifconfig bond0 down
-# rmmod bonding
-# rmmod e100
-
- Again, for convenience, it may be desirable to create a script
-with these commands.
-
-
-3.3.1 Configuring Multiple Bonds Manually
------------------------------------------
-
- This section contains information on configuring multiple
-bonding devices with differing options for those systems whose network
-initialization scripts lack support for configuring multiple bonds.
-
- If you require multiple bonding devices, but all with the same
-options, you may wish to use the "max_bonds" module parameter,
-documented above.
-
- To create multiple bonding devices with differing options, it is
-preferrable to use bonding parameters exported by sysfs, documented in the
-section below.
-
- For versions of bonding without sysfs support, the only means to
-provide multiple instances of bonding with differing options is to load
-the bonding driver multiple times. Note that current versions of the
-sysconfig network initialization scripts handle this automatically; if
-your distro uses these scripts, no special action is needed. See the
-section Configuring Bonding Devices, above, if you're not sure about your
-network initialization scripts.
-
- To load multiple instances of the module, it is necessary to
-specify a different name for each instance (the module loading system
-requires that every loaded module, even multiple instances of the same
-module, have a unique name). This is accomplished by supplying multiple
-sets of bonding options in /etc/modprobe.d/*.conf, for example:
-
-alias bond0 bonding
-options bond0 -o bond0 mode=balance-rr miimon=100
-
-alias bond1 bonding
-options bond1 -o bond1 mode=balance-alb miimon=50
-
- will load the bonding module two times. The first instance is
-named "bond0" and creates the bond0 device in balance-rr mode with an
-miimon of 100. The second instance is named "bond1" and creates the
-bond1 device in balance-alb mode with an miimon of 50.
-
- In some circumstances (typically with older distributions),
-the above does not work, and the second bonding instance never sees
-its options. In that case, the second options line can be substituted
-as follows:
-
-install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
- mode=balance-alb miimon=50
-
- This may be repeated any number of times, specifying a new and
-unique name in place of bond1 for each subsequent instance.
-
- It has been observed that some Red Hat supplied kernels are unable
-to rename modules at load time (the "-o bond1" part). Attempts to pass
-that option to modprobe will produce an "Operation not permitted" error.
-This has been reported on some Fedora Core kernels, and has been seen on
-RHEL 4 as well. On kernels exhibiting this problem, it will be impossible
-to configure multiple bonds with differing parameters (as they are older
-kernels, and also lack sysfs support).
-
-3.4 Configuring Bonding Manually via Sysfs
-------------------------------------------
-
- Starting with version 3.0.0, Channel Bonding may be configured
-via the sysfs interface. This interface allows dynamic configuration
-of all bonds in the system without unloading the module. It also
-allows for adding and removing bonds at runtime. Ifenslave is no
-longer required, though it is still supported.
-
- Use of the sysfs interface allows you to use multiple bonds
-with different configurations without having to reload the module.
-It also allows you to use multiple, differently configured bonds when
-bonding is compiled into the kernel.
-
- You must have the sysfs filesystem mounted to configure
-bonding this way. The examples in this document assume that you
-are using the standard mount point for sysfs, e.g. /sys. If your
-sysfs filesystem is mounted elsewhere, you will need to adjust the
-example paths accordingly.
-
-Creating and Destroying Bonds
------------------------------
-To add a new bond foo:
-# echo +foo > /sys/class/net/bonding_masters
-
-To remove an existing bond bar:
-# echo -bar > /sys/class/net/bonding_masters
-
-To show all existing bonds:
-# cat /sys/class/net/bonding_masters
-
-NOTE: due to 4K size limitation of sysfs files, this list may be
-truncated if you have more than a few hundred bonds. This is unlikely
-to occur under normal operating conditions.
-
-Adding and Removing Slaves
---------------------------
- Interfaces may be enslaved to a bond using the file
-/sys/class/net/<bond>/bonding/slaves. The semantics for this file
-are the same as for the bonding_masters file.
-
-To enslave interface eth0 to bond bond0:
-# ifconfig bond0 up
-# echo +eth0 > /sys/class/net/bond0/bonding/slaves
-
-To free slave eth0 from bond bond0:
-# echo -eth0 > /sys/class/net/bond0/bonding/slaves
-
- When an interface is enslaved to a bond, symlinks between the
-two are created in the sysfs filesystem. In this case, you would get
-/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
-/sys/class/net/eth0/master pointing to /sys/class/net/bond0.
-
- This means that you can tell quickly whether or not an
-interface is enslaved by looking for the master symlink. Thus:
-# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
-will free eth0 from whatever bond it is enslaved to, regardless of
-the name of the bond interface.
-
-Changing a Bond's Configuration
--------------------------------
- Each bond may be configured individually by manipulating the
-files located in /sys/class/net/<bond name>/bonding
-
- The names of these files correspond directly with the command-
-line parameters described elsewhere in this file, and, with the
-exception of arp_ip_target, they accept the same values. To see the
-current setting, simply cat the appropriate file.
-
- A few examples will be given here; for specific usage
-guidelines for each parameter, see the appropriate section in this
-document.
-
-To configure bond0 for balance-alb mode:
-# ifconfig bond0 down
-# echo 6 > /sys/class/net/bond0/bonding/mode
- - or -
-# echo balance-alb > /sys/class/net/bond0/bonding/mode
- NOTE: The bond interface must be down before the mode can be
-changed.
-
-To enable MII monitoring on bond0 with a 1 second interval:
-# echo 1000 > /sys/class/net/bond0/bonding/miimon
- NOTE: If ARP monitoring is enabled, it will disabled when MII
-monitoring is enabled, and vice-versa.
-
-To add ARP targets:
-# echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
-# echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target
- NOTE: up to 16 target addresses may be specified.
-
-To remove an ARP target:
-# echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
-
-Example Configuration
----------------------
- We begin with the same example that is shown in section 3.3,
-executed with sysfs, and without using ifenslave.
-
- To make a simple bond of two e100 devices (presumed to be eth0
-and eth1), and have it persist across reboots, edit the appropriate
-file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
-following:
-
-modprobe bonding
-modprobe e100
-echo balance-alb > /sys/class/net/bond0/bonding/mode
-ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
-echo 100 > /sys/class/net/bond0/bonding/miimon
-echo +eth0 > /sys/class/net/bond0/bonding/slaves
-echo +eth1 > /sys/class/net/bond0/bonding/slaves
-
- To add a second bond, with two e1000 interfaces in
-active-backup mode, using ARP monitoring, add the following lines to
-your init script:
-
-modprobe e1000
-echo +bond1 > /sys/class/net/bonding_masters
-echo active-backup > /sys/class/net/bond1/bonding/mode
-ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up
-echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target
-echo 2000 > /sys/class/net/bond1/bonding/arp_interval
-echo +eth2 > /sys/class/net/bond1/bonding/slaves
-echo +eth3 > /sys/class/net/bond1/bonding/slaves
-
-3.5 Configuration with Interfaces Support
------------------------------------------
-
- This section applies to distros which use /etc/network/interfaces file
-to describe network interface configuration, most notably Debian and it's
-derivatives.
-
- The ifup and ifdown commands on Debian don't support bonding out of
-the box. The ifenslave-2.6 package should be installed to provide bonding
-support. Once installed, this package will provide bond-* options to be used
-into /etc/network/interfaces.
-
- Note that ifenslave-2.6 package will load the bonding module and use
-the ifenslave command when appropriate.
-
-Example Configurations
-----------------------
-
-In /etc/network/interfaces, the following stanza will configure bond0, in
-active-backup mode, with eth0 and eth1 as slaves.
-
-auto bond0
-iface bond0 inet dhcp
- bond-slaves eth0 eth1
- bond-mode active-backup
- bond-miimon 100
- bond-primary eth0 eth1
-
-If the above configuration doesn't work, you might have a system using
-upstart for system startup. This is most notably true for recent
-Ubuntu versions. The following stanza in /etc/network/interfaces will
-produce the same result on those systems.
-
-auto bond0
-iface bond0 inet dhcp
- bond-slaves none
- bond-mode active-backup
- bond-miimon 100
-
-auto eth0
-iface eth0 inet manual
- bond-master bond0
- bond-primary eth0 eth1
-
-auto eth1
-iface eth1 inet manual
- bond-master bond0
- bond-primary eth0 eth1
-
-For a full list of bond-* supported options in /etc/network/interfaces and some
-more advanced examples tailored to you particular distros, see the files in
-/usr/share/doc/ifenslave-2.6.
-
-3.6 Overriding Configuration for Special Cases
-----------------------------------------------
-
-When using the bonding driver, the physical port which transmits a frame is
-typically selected by the bonding driver, and is not relevant to the user or
-system administrator. The output port is simply selected using the policies of
-the selected bonding mode. On occasion however, it is helpful to direct certain
-classes of traffic to certain physical interfaces on output to implement
-slightly more complex policies. For example, to reach a web server over a
-bonded interface in which eth0 connects to a private network, while eth1
-connects via a public network, it may be desirous to bias the bond to send said
-traffic over eth0 first, using eth1 only as a fall back, while all other traffic
-can safely be sent over either interface. Such configurations may be achieved
-using the traffic control utilities inherent in linux.
-
-By default the bonding driver is multiqueue aware and 16 queues are created
-when the driver initializes (see Documentation/networking/multiqueue.txt
-for details). If more or less queues are desired the module parameter
-tx_queues can be used to change this value. There is no sysfs parameter
-available as the allocation is done at module init time.
-
-The output of the file /proc/net/bonding/bondX has changed so the output Queue
-ID is now printed for each slave:
-
-Bonding Mode: fault-tolerance (active-backup)
-Primary Slave: None
-Currently Active Slave: eth0
-MII Status: up
-MII Polling Interval (ms): 0
-Up Delay (ms): 0
-Down Delay (ms): 0
-
-Slave Interface: eth0
-MII Status: up
-Link Failure Count: 0
-Permanent HW addr: 00:1a:a0:12:8f:cb
-Slave queue ID: 0
-
-Slave Interface: eth1
-MII Status: up
-Link Failure Count: 0
-Permanent HW addr: 00:1a:a0:12:8f:cc
-Slave queue ID: 2
-
-The queue_id for a slave can be set using the command:
-
-# echo "eth1:2" > /sys/class/net/bond0/bonding/queue_id
-
-Any interface that needs a queue_id set should set it with multiple calls
-like the one above until proper priorities are set for all interfaces. On
-distributions that allow configuration via initscripts, multiple 'queue_id'
-arguments can be added to BONDING_OPTS to set all needed slave queues.
-
-These queue id's can be used in conjunction with the tc utility to configure
-a multiqueue qdisc and filters to bias certain traffic to transmit on certain
-slave devices. For instance, say we wanted, in the above configuration to
-force all traffic bound to 192.168.1.100 to use eth1 in the bond as its output
-device. The following commands would accomplish this:
-
-# tc qdisc add dev bond0 handle 1 root multiq
-
-# tc filter add dev bond0 protocol ip parent 1: prio 1 u32 match ip dst \
- 192.168.1.100 action skbedit queue_mapping 2
-
-These commands tell the kernel to attach a multiqueue queue discipline to the
-bond0 interface and filter traffic enqueued to it, such that packets with a dst
-ip of 192.168.1.100 have their output queue mapping value overwritten to 2.
-This value is then passed into the driver, causing the normal output path
-selection policy to be overridden, selecting instead qid 2, which maps to eth1.
-
-Note that qid values begin at 1. Qid 0 is reserved to initiate to the driver
-that normal output policy selection should take place. One benefit to simply
-leaving the qid for a slave to 0 is the multiqueue awareness in the bonding
-driver that is now present. This awareness allows tc filters to be placed on
-slave devices as well as bond devices and the bonding driver will simply act as
-a pass-through for selecting output queues on the slave device rather than
-output port selection.
-
-This feature first appeared in bonding driver version 3.7.0 and support for
-output slave selection was limited to round-robin and active-backup modes.
-
-4 Querying Bonding Configuration
-=================================
-
-4.1 Bonding Configuration
--------------------------
-
- Each bonding device has a read-only file residing in the
-/proc/net/bonding directory. The file contents include information
-about the bonding configuration, options and state of each slave.
-
- For example, the contents of /proc/net/bonding/bond0 after the
-driver is loaded with parameters of mode=0 and miimon=1000 is
-generally as follows:
-
- Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
- Bonding Mode: load balancing (round-robin)
- Currently Active Slave: eth0
- MII Status: up
- MII Polling Interval (ms): 1000
- Up Delay (ms): 0
- Down Delay (ms): 0
-
- Slave Interface: eth1
- MII Status: up
- Link Failure Count: 1
-
- Slave Interface: eth0
- MII Status: up
- Link Failure Count: 1
-
- The precise format and contents will change depending upon the
-bonding configuration, state, and version of the bonding driver.
-
-4.2 Network configuration
--------------------------
-
- The network configuration can be inspected using the ifconfig
-command. Bonding devices will have the MASTER flag set; Bonding slave
-devices will have the SLAVE flag set. The ifconfig output does not
-contain information on which slaves are associated with which masters.
-
- In the example below, the bond0 interface is the master
-(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
-bond0 have the same MAC address (HWaddr) as bond0 for all modes except
-TLB and ALB that require a unique MAC address for each slave.
-
-# /sbin/ifconfig
-bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
- inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
- UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
- RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
- TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
- collisions:0 txqueuelen:0
-
-eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
- UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
- RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
- TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
- collisions:0 txqueuelen:100
- Interrupt:10 Base address:0x1080
-
-eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
- UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
- RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
- TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
- collisions:0 txqueuelen:100
- Interrupt:9 Base address:0x1400
-
-5. Switch Configuration
-=======================
-
- For this section, "switch" refers to whatever system the
-bonded devices are directly connected to (i.e., where the other end of
-the cable plugs into). This may be an actual dedicated switch device,
-or it may be another regular system (e.g., another computer running
-Linux),
-
- The active-backup, balance-tlb and balance-alb modes do not
-require any specific configuration of the switch.
-
- The 802.3ad mode requires that the switch have the appropriate
-ports configured as an 802.3ad aggregation. The precise method used
-to configure this varies from switch to switch, but, for example, a
-Cisco 3550 series switch requires that the appropriate ports first be
-grouped together in a single etherchannel instance, then that
-etherchannel is set to mode "lacp" to enable 802.3ad (instead of
-standard EtherChannel).
-
- The balance-rr, balance-xor and broadcast modes generally
-require that the switch have the appropriate ports grouped together.
-The nomenclature for such a group differs between switches, it may be
-called an "etherchannel" (as in the Cisco example, above), a "trunk
-group" or some other similar variation. For these modes, each switch
-will also have its own configuration options for the switch's transmit
-policy to the bond. Typical choices include XOR of either the MAC or
-IP addresses. The transmit policy of the two peers does not need to
-match. For these three modes, the bonding mode really selects a
-transmit policy for an EtherChannel group; all three will interoperate
-with another EtherChannel group.
-
-
-6. 802.1q VLAN Support
-======================
-
- It is possible to configure VLAN devices over a bond interface
-using the 8021q driver. However, only packets coming from the 8021q
-driver and passing through bonding will be tagged by default. Self
-generated packets, for example, bonding's learning packets or ARP
-packets generated by either ALB mode or the ARP monitor mechanism, are
-tagged internally by bonding itself. As a result, bonding must
-"learn" the VLAN IDs configured above it, and use those IDs to tag
-self generated packets.
-
- For reasons of simplicity, and to support the use of adapters
-that can do VLAN hardware acceleration offloading, the bonding
-interface declares itself as fully hardware offloading capable, it gets
-the add_vid/kill_vid notifications to gather the necessary
-information, and it propagates those actions to the slaves. In case
-of mixed adapter types, hardware accelerated tagged packets that
-should go through an adapter that is not offloading capable are
-"un-accelerated" by the bonding driver so the VLAN tag sits in the
-regular location.
-
- VLAN interfaces *must* be added on top of a bonding interface
-only after enslaving at least one slave. The bonding interface has a
-hardware address of 00:00:00:00:00:00 until the first slave is added.
-If the VLAN interface is created prior to the first enslavement, it
-would pick up the all-zeroes hardware address. Once the first slave
-is attached to the bond, the bond device itself will pick up the
-slave's hardware address, which is then available for the VLAN device.
-
- Also, be aware that a similar problem can occur if all slaves
-are released from a bond that still has one or more VLAN interfaces on
-top of it. When a new slave is added, the bonding interface will
-obtain its hardware address from the first slave, which might not
-match the hardware address of the VLAN interfaces (which was
-ultimately copied from an earlier slave).
-
- There are two methods to insure that the VLAN device operates
-with the correct hardware address if all slaves are removed from a
-bond interface:
-
- 1. Remove all VLAN interfaces then recreate them
-
- 2. Set the bonding interface's hardware address so that it
-matches the hardware address of the VLAN interfaces.
-
- Note that changing a VLAN interface's HW address would set the
-underlying device -- i.e. the bonding interface -- to promiscuous
-mode, which might not be what you want.
-
-
-7. Link Monitoring
-==================
-
- The bonding driver at present supports two schemes for
-monitoring a slave device's link state: the ARP monitor and the MII
-monitor.
-
- At the present time, due to implementation restrictions in the
-bonding driver itself, it is not possible to enable both ARP and MII
-monitoring simultaneously.
-
-7.1 ARP Monitor Operation
--------------------------
-
- The ARP monitor operates as its name suggests: it sends ARP
-queries to one or more designated peer systems on the network, and
-uses the response as an indication that the link is operating. This
-gives some assurance that traffic is actually flowing to and from one
-or more peers on the local network.
-
- The ARP monitor relies on the device driver itself to verify
-that traffic is flowing. In particular, the driver must keep up to
-date the last receive time, dev->last_rx, and transmit start time,
-dev->trans_start. If these are not updated by the driver, then the
-ARP monitor will immediately fail any slaves using that driver, and
-those slaves will stay down. If networking monitoring (tcpdump, etc)
-shows the ARP requests and replies on the network, then it may be that
-your device driver is not updating last_rx and trans_start.
-
-7.2 Configuring Multiple ARP Targets
-------------------------------------
-
- While ARP monitoring can be done with just one target, it can
-be useful in a High Availability setup to have several targets to
-monitor. In the case of just one target, the target itself may go
-down or have a problem making it unresponsive to ARP requests. Having
-an additional target (or several) increases the reliability of the ARP
-monitoring.
-
- Multiple ARP targets must be separated by commas as follows:
-
-# example options for ARP monitoring with three targets
-alias bond0 bonding
-options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
-
- For just a single target the options would resemble:
-
-# example options for ARP monitoring with one target
-alias bond0 bonding
-options bond0 arp_interval=60 arp_ip_target=192.168.0.100
-
-
-7.3 MII Monitor Operation
--------------------------
-
- The MII monitor monitors only the carrier state of the local
-network interface. It accomplishes this in one of three ways: by
-depending upon the device driver to maintain its carrier state, by
-querying the device's MII registers, or by making an ethtool query to
-the device.
-
- If the use_carrier module parameter is 1 (the default value),
-then the MII monitor will rely on the driver for carrier state
-information (via the netif_carrier subsystem). As explained in the
-use_carrier parameter information, above, if the MII monitor fails to
-detect carrier loss on the device (e.g., when the cable is physically
-disconnected), it may be that the driver does not support
-netif_carrier.
-
- If use_carrier is 0, then the MII monitor will first query the
-device's (via ioctl) MII registers and check the link state. If that
-request fails (not just that it returns carrier down), then the MII
-monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain
-the same information. If both methods fail (i.e., the driver either
-does not support or had some error in processing both the MII register
-and ethtool requests), then the MII monitor will assume the link is
-up.
-
-8. Potential Sources of Trouble
-===============================
-
-8.1 Adventures in Routing
--------------------------
-
- When bonding is configured, it is important that the slave
-devices not have routes that supersede routes of the master (or,
-generally, not have routes at all). For example, suppose the bonding
-device bond0 has two slaves, eth0 and eth1, and the routing table is
-as follows:
-
-Kernel IP routing table
-Destination Gateway Genmask Flags MSS Window irtt Iface
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
-10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
-127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
-
- This routing configuration will likely still update the
-receive/transmit times in the driver (needed by the ARP monitor), but
-may bypass the bonding driver (because outgoing traffic to, in this
-case, another host on network 10 would use eth0 or eth1 before bond0).
-
- The ARP monitor (and ARP itself) may become confused by this
-configuration, because ARP requests (generated by the ARP monitor)
-will be sent on one interface (bond0), but the corresponding reply
-will arrive on a different interface (eth0). This reply looks to ARP
-as an unsolicited ARP reply (because ARP matches replies on an
-interface basis), and is discarded. The MII monitor is not affected
-by the state of the routing table.
-
- The solution here is simply to insure that slaves do not have
-routes of their own, and if for some reason they must, those routes do
-not supersede routes of their master. This should generally be the
-case, but unusual configurations or errant manual or automatic static
-route additions may cause trouble.
-
-8.2 Ethernet Device Renaming
-----------------------------
-
- On systems with network configuration scripts that do not
-associate physical devices directly with network interface names (so
-that the same physical device always has the same "ethX" name), it may
-be necessary to add some special logic to config files in
-/etc/modprobe.d/.
-
- For example, given a modules.conf containing the following:
-
-alias bond0 bonding
-options bond0 mode=some-mode miimon=50
-alias eth0 tg3
-alias eth1 tg3
-alias eth2 e1000
-alias eth3 e1000
-
- If neither eth0 and eth1 are slaves to bond0, then when the
-bond0 interface comes up, the devices may end up reordered. This
-happens because bonding is loaded first, then its slave device's
-drivers are loaded next. Since no other drivers have been loaded,
-when the e1000 driver loads, it will receive eth0 and eth1 for its
-devices, but the bonding configuration tries to enslave eth2 and eth3
-(which may later be assigned to the tg3 devices).
-
- Adding the following:
-
-add above bonding e1000 tg3
-
- causes modprobe to load e1000 then tg3, in that order, when
-bonding is loaded. This command is fully documented in the
-modules.conf manual page.
-
- On systems utilizing modprobe an equivalent problem can occur.
-In this case, the following can be added to config files in
-/etc/modprobe.d/ as:
-
-softdep bonding pre: tg3 e1000
-
- This will load tg3 and e1000 modules before loading the bonding one.
-Full documentation on this can be found in the modprobe.d and modprobe
-manual pages.
-
-8.3. Painfully Slow Or No Failed Link Detection By Miimon
----------------------------------------------------------
-
- By default, bonding enables the use_carrier option, which
-instructs bonding to trust the driver to maintain carrier state.
-
- As discussed in the options section, above, some drivers do
-not support the netif_carrier_on/_off link state tracking system.
-With use_carrier enabled, bonding will always see these links as up,
-regardless of their actual state.
-
- Additionally, other drivers do support netif_carrier, but do
-not maintain it in real time, e.g., only polling the link state at
-some fixed interval. In this case, miimon will detect failures, but
-only after some long period of time has expired. If it appears that
-miimon is very slow in detecting link failures, try specifying
-use_carrier=0 to see if that improves the failure detection time. If
-it does, then it may be that the driver checks the carrier state at a
-fixed interval, but does not cache the MII register values (so the
-use_carrier=0 method of querying the registers directly works). If
-use_carrier=0 does not improve the failover, then the driver may cache
-the registers, or the problem may be elsewhere.
-
- Also, remember that miimon only checks for the device's
-carrier state. It has no way to determine the state of devices on or
-beyond other ports of a switch, or if a switch is refusing to pass
-traffic while still maintaining carrier on.
-
-9. SNMP agents
-===============
-
- If running SNMP agents, the bonding driver should be loaded
-before any network drivers participating in a bond. This requirement
-is due to the interface index (ipAdEntIfIndex) being associated to
-the first interface found with a given IP address. That is, there is
-only one ipAdEntIfIndex for each IP address. For example, if eth0 and
-eth1 are slaves of bond0 and the driver for eth0 is loaded before the
-bonding driver, the interface for the IP address will be associated
-with the eth0 interface. This configuration is shown below, the IP
-address 192.168.1.1 has an interface index of 2 which indexes to eth0
-in the ifDescr table (ifDescr.2).
-
- interfaces.ifTable.ifEntry.ifDescr.1 = lo
- interfaces.ifTable.ifEntry.ifDescr.2 = eth0
- interfaces.ifTable.ifEntry.ifDescr.3 = eth1
- interfaces.ifTable.ifEntry.ifDescr.4 = eth2
- interfaces.ifTable.ifEntry.ifDescr.5 = eth3
- interfaces.ifTable.ifEntry.ifDescr.6 = bond0
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
-
- This problem is avoided by loading the bonding driver before
-any network drivers participating in a bond. Below is an example of
-loading the bonding driver first, the IP address 192.168.1.1 is
-correctly associated with ifDescr.2.
-
- interfaces.ifTable.ifEntry.ifDescr.1 = lo
- interfaces.ifTable.ifEntry.ifDescr.2 = bond0
- interfaces.ifTable.ifEntry.ifDescr.3 = eth0
- interfaces.ifTable.ifEntry.ifDescr.4 = eth1
- interfaces.ifTable.ifEntry.ifDescr.5 = eth2
- interfaces.ifTable.ifEntry.ifDescr.6 = eth3
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
- ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
-
- While some distributions may not report the interface name in
-ifDescr, the association between the IP address and IfIndex remains
-and SNMP functions such as Interface_Scan_Next will report that
-association.
-
-10. Promiscuous mode
-====================
-
- When running network monitoring tools, e.g., tcpdump, it is
-common to enable promiscuous mode on the device, so that all traffic
-is seen (instead of seeing only traffic destined for the local host).
-The bonding driver handles promiscuous mode changes to the bonding
-master device (e.g., bond0), and propagates the setting to the slave
-devices.
-
- For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
-the promiscuous mode setting is propagated to all slaves.
-
- For the active-backup, balance-tlb and balance-alb modes, the
-promiscuous mode setting is propagated only to the active slave.
-
- For balance-tlb mode, the active slave is the slave currently
-receiving inbound traffic.
-
- For balance-alb mode, the active slave is the slave used as a
-"primary." This slave is used for mode-specific control traffic, for
-sending to peers that are unassigned or if the load is unbalanced.
-
- For the active-backup, balance-tlb and balance-alb modes, when
-the active slave changes (e.g., due to a link failure), the
-promiscuous setting will be propagated to the new active slave.
-
-11. Configuring Bonding for High Availability
-=============================================
-
- High Availability refers to configurations that provide
-maximum network availability by having redundant or backup devices,
-links or switches between the host and the rest of the world. The
-goal is to provide the maximum availability of network connectivity
-(i.e., the network always works), even though other configurations
-could provide higher throughput.
-
-11.1 High Availability in a Single Switch Topology
---------------------------------------------------
-
- If two hosts (or a host and a single switch) are directly
-connected via multiple physical links, then there is no availability
-penalty to optimizing for maximum bandwidth. In this case, there is
-only one switch (or peer), so if it fails, there is no alternative
-access to fail over to. Additionally, the bonding load balance modes
-support link monitoring of their members, so if individual links fail,
-the load will be rebalanced across the remaining devices.
-
- See Section 13, "Configuring Bonding for Maximum Throughput"
-for information on configuring bonding with one peer device.
-
-11.2 High Availability in a Multiple Switch Topology
-----------------------------------------------------
-
- With multiple switches, the configuration of bonding and the
-network changes dramatically. In multiple switch topologies, there is
-a trade off between network availability and usable bandwidth.
-
- Below is a sample network, configured to maximize the
-availability of the network:
-
- | |
- |port3 port3|
- +-----+----+ +-----+----+
- | |port2 ISL port2| |
- | switch A +--------------------------+ switch B |
- | | | |
- +-----+----+ +-----++---+
- |port1 port1|
- | +-------+ |
- +-------------+ host1 +---------------+
- eth0 +-------+ eth1
-
- In this configuration, there is a link between the two
-switches (ISL, or inter switch link), and multiple ports connecting to
-the outside world ("port3" on each switch). There is no technical
-reason that this could not be extended to a third switch.
-
-11.2.1 HA Bonding Mode Selection for Multiple Switch Topology
--------------------------------------------------------------
-
- In a topology such as the example above, the active-backup and
-broadcast modes are the only useful bonding modes when optimizing for
-availability; the other modes require all links to terminate on the
-same peer for them to behave rationally.
-
-active-backup: This is generally the preferred mode, particularly if
- the switches have an ISL and play together well. If the
- network configuration is such that one switch is specifically
- a backup switch (e.g., has lower capacity, higher cost, etc),
- then the primary option can be used to insure that the
- preferred link is always used when it is available.
-
-broadcast: This mode is really a special purpose mode, and is suitable
- only for very specific needs. For example, if the two
- switches are not connected (no ISL), and the networks beyond
- them are totally independent. In this case, if it is
- necessary for some specific one-way traffic to reach both
- independent networks, then the broadcast mode may be suitable.
-
-11.2.2 HA Link Monitoring Selection for Multiple Switch Topology
-----------------------------------------------------------------
-
- The choice of link monitoring ultimately depends upon your
-switch. If the switch can reliably fail ports in response to other
-failures, then either the MII or ARP monitors should work. For
-example, in the above example, if the "port3" link fails at the remote
-end, the MII monitor has no direct means to detect this. The ARP
-monitor could be configured with a target at the remote end of port3,
-thus detecting that failure without switch support.
-
- In general, however, in a multiple switch topology, the ARP
-monitor can provide a higher level of reliability in detecting end to
-end connectivity failures (which may be caused by the failure of any
-individual component to pass traffic for any reason). Additionally,
-the ARP monitor should be configured with multiple targets (at least
-one for each switch in the network). This will insure that,
-regardless of which switch is active, the ARP monitor has a suitable
-target to query.
-
- Note, also, that of late many switches now support a functionality
-generally referred to as "trunk failover." This is a feature of the
-switch that causes the link state of a particular switch port to be set
-down (or up) when the state of another switch port goes down (or up).
-Its purpose is to propagate link failures from logically "exterior" ports
-to the logically "interior" ports that bonding is able to monitor via
-miimon. Availability and configuration for trunk failover varies by
-switch, but this can be a viable alternative to the ARP monitor when using
-suitable switches.
-
-12. Configuring Bonding for Maximum Throughput
-==============================================
-
-12.1 Maximizing Throughput in a Single Switch Topology
-------------------------------------------------------
-
- In a single switch configuration, the best method to maximize
-throughput depends upon the application and network environment. The
-various load balancing modes each have strengths and weaknesses in
-different environments, as detailed below.
-
- For this discussion, we will break down the topologies into
-two categories. Depending upon the destination of most traffic, we
-categorize them into either "gatewayed" or "local" configurations.
-
- In a gatewayed configuration, the "switch" is acting primarily
-as a router, and the majority of traffic passes through this router to
-other networks. An example would be the following:
-
-
- +----------+ +----------+
- | |eth0 port1| | to other networks
- | Host A +---------------------+ router +------------------->
- | +---------------------+ | Hosts B and C are out
- | |eth1 port2| | here somewhere
- +----------+ +----------+
-
- The router may be a dedicated router device, or another host
-acting as a gateway. For our discussion, the important point is that
-the majority of traffic from Host A will pass through the router to
-some other network before reaching its final destination.
-
- In a gatewayed network configuration, although Host A may
-communicate with many other systems, all of its traffic will be sent
-and received via one other peer on the local network, the router.
-
- Note that the case of two systems connected directly via
-multiple physical links is, for purposes of configuring bonding, the
-same as a gatewayed configuration. In that case, it happens that all
-traffic is destined for the "gateway" itself, not some other network
-beyond the gateway.
-
- In a local configuration, the "switch" is acting primarily as
-a switch, and the majority of traffic passes through this switch to
-reach other stations on the same network. An example would be the
-following:
-
- +----------+ +----------+ +--------+
- | |eth0 port1| +-------+ Host B |
- | Host A +------------+ switch |port3 +--------+
- | +------------+ | +--------+
- | |eth1 port2| +------------------+ Host C |
- +----------+ +----------+port4 +--------+
-
-
- Again, the switch may be a dedicated switch device, or another
-host acting as a gateway. For our discussion, the important point is
-that the majority of traffic from Host A is destined for other hosts
-on the same local network (Hosts B and C in the above example).
-
- In summary, in a gatewayed configuration, traffic to and from
-the bonded device will be to the same MAC level peer on the network
-(the gateway itself, i.e., the router), regardless of its final
-destination. In a local configuration, traffic flows directly to and
-from the final destinations, thus, each destination (Host B, Host C)
-will be addressed directly by their individual MAC addresses.
-
- This distinction between a gatewayed and a local network
-configuration is important because many of the load balancing modes
-available use the MAC addresses of the local network source and
-destination to make load balancing decisions. The behavior of each
-mode is described below.
-
-
-12.1.1 MT Bonding Mode Selection for Single Switch Topology
------------------------------------------------------------
-
- This configuration is the easiest to set up and to understand,
-although you will have to decide which bonding mode best suits your
-needs. The trade offs for each mode are detailed below:
-
-balance-rr: This mode is the only mode that will permit a single
- TCP/IP connection to stripe traffic across multiple
- interfaces. It is therefore the only mode that will allow a
- single TCP/IP stream to utilize more than one interface's
- worth of throughput. This comes at a cost, however: the
- striping generally results in peer systems receiving packets out
- of order, causing TCP/IP's congestion control system to kick
- in, often by retransmitting segments.
-
- It is possible to adjust TCP/IP's congestion limits by
- altering the net.ipv4.tcp_reordering sysctl parameter. The
- usual default value is 3, and the maximum useful value is 127.
- For a four interface balance-rr bond, expect that a single
- TCP/IP stream will utilize no more than approximately 2.3
- interface's worth of throughput, even after adjusting
- tcp_reordering.
-
- Note that the fraction of packets that will be delivered out of
- order is highly variable, and is unlikely to be zero. The level
- of reordering depends upon a variety of factors, including the
- networking interfaces, the switch, and the topology of the
- configuration. Speaking in general terms, higher speed network
- cards produce more reordering (due to factors such as packet
- coalescing), and a "many to many" topology will reorder at a
- higher rate than a "many slow to one fast" configuration.
-
- Many switches do not support any modes that stripe traffic
- (instead choosing a port based upon IP or MAC level addresses);
- for those devices, traffic for a particular connection flowing
- through the switch to a balance-rr bond will not utilize greater
- than one interface's worth of bandwidth.
-
- If you are utilizing protocols other than TCP/IP, UDP for
- example, and your application can tolerate out of order
- delivery, then this mode can allow for single stream datagram
- performance that scales near linearly as interfaces are added
- to the bond.
-
- This mode requires the switch to have the appropriate ports
- configured for "etherchannel" or "trunking."
-
-active-backup: There is not much advantage in this network topology to
- the active-backup mode, as the inactive backup devices are all
- connected to the same peer as the primary. In this case, a
- load balancing mode (with link monitoring) will provide the
- same level of network availability, but with increased
- available bandwidth. On the plus side, active-backup mode
- does not require any configuration of the switch, so it may
- have value if the hardware available does not support any of
- the load balance modes.
-
-balance-xor: This mode will limit traffic such that packets destined
- for specific peers will always be sent over the same
- interface. Since the destination is determined by the MAC
- addresses involved, this mode works best in a "local" network
- configuration (as described above), with destinations all on
- the same local network. This mode is likely to be suboptimal
- if all your traffic is passed through a single router (i.e., a
- "gatewayed" network configuration, as described above).
-
- As with balance-rr, the switch ports need to be configured for
- "etherchannel" or "trunking."
-
-broadcast: Like active-backup, there is not much advantage to this
- mode in this type of network topology.
-
-802.3ad: This mode can be a good choice for this type of network
- topology. The 802.3ad mode is an IEEE standard, so all peers
- that implement 802.3ad should interoperate well. The 802.3ad
- protocol includes automatic configuration of the aggregates,
- so minimal manual configuration of the switch is needed
- (typically only to designate that some set of devices is
- available for 802.3ad). The 802.3ad standard also mandates
- that frames be delivered in order (within certain limits), so
- in general single connections will not see misordering of
- packets. The 802.3ad mode does have some drawbacks: the
- standard mandates that all devices in the aggregate operate at
- the same speed and duplex. Also, as with all bonding load
- balance modes other than balance-rr, no single connection will
- be able to utilize more than a single interface's worth of
- bandwidth.
-
- Additionally, the linux bonding 802.3ad implementation
- distributes traffic by peer (using an XOR of MAC addresses),
- so in a "gatewayed" configuration, all outgoing traffic will
- generally use the same device. Incoming traffic may also end
- up on a single device, but that is dependent upon the
- balancing policy of the peer's 8023.ad implementation. In a
- "local" configuration, traffic will be distributed across the
- devices in the bond.
-
- Finally, the 802.3ad mode mandates the use of the MII monitor,
- therefore, the ARP monitor is not available in this mode.
-
-balance-tlb: The balance-tlb mode balances outgoing traffic by peer.
- Since the balancing is done according to MAC address, in a
- "gatewayed" configuration (as described above), this mode will
- send all traffic across a single device. However, in a
- "local" network configuration, this mode balances multiple
- local network peers across devices in a vaguely intelligent
- manner (not a simple XOR as in balance-xor or 802.3ad mode),
- so that mathematically unlucky MAC addresses (i.e., ones that
- XOR to the same value) will not all "bunch up" on a single
- interface.
-
- Unlike 802.3ad, interfaces may be of differing speeds, and no
- special switch configuration is required. On the down side,
- in this mode all incoming traffic arrives over a single
- interface, this mode requires certain ethtool support in the
- network device driver of the slave interfaces, and the ARP
- monitor is not available.
-
-balance-alb: This mode is everything that balance-tlb is, and more.
- It has all of the features (and restrictions) of balance-tlb,
- and will also balance incoming traffic from local network
- peers (as described in the Bonding Module Options section,
- above).
-
- The only additional down side to this mode is that the network
- device driver must support changing the hardware address while
- the device is open.
-
-12.1.2 MT Link Monitoring for Single Switch Topology
-----------------------------------------------------
-
- The choice of link monitoring may largely depend upon which
-mode you choose to use. The more advanced load balancing modes do not
-support the use of the ARP monitor, and are thus restricted to using
-the MII monitor (which does not provide as high a level of end to end
-assurance as the ARP monitor).
-
-12.2 Maximum Throughput in a Multiple Switch Topology
------------------------------------------------------
-
- Multiple switches may be utilized to optimize for throughput
-when they are configured in parallel as part of an isolated network
-between two or more systems, for example:
-
- +-----------+
- | Host A |
- +-+---+---+-+
- | | |
- +--------+ | +---------+
- | | |
- +------+---+ +-----+----+ +-----+----+
- | Switch A | | Switch B | | Switch C |
- +------+---+ +-----+----+ +-----+----+
- | | |
- +--------+ | +---------+
- | | |
- +-+---+---+-+
- | Host B |
- +-----------+
-
- In this configuration, the switches are isolated from one
-another. One reason to employ a topology such as this is for an
-isolated network with many hosts (a cluster configured for high
-performance, for example), using multiple smaller switches can be more
-cost effective than a single larger switch, e.g., on a network with 24
-hosts, three 24 port switches can be significantly less expensive than
-a single 72 port switch.
-
- If access beyond the network is required, an individual host
-can be equipped with an additional network device connected to an
-external network; this host then additionally acts as a gateway.
-
-12.2.1 MT Bonding Mode Selection for Multiple Switch Topology
--------------------------------------------------------------
-
- In actual practice, the bonding mode typically employed in
-configurations of this type is balance-rr. Historically, in this
-network configuration, the usual caveats about out of order packet
-delivery are mitigated by the use of network adapters that do not do
-any kind of packet coalescing (via the use of NAPI, or because the
-device itself does not generate interrupts until some number of
-packets has arrived). When employed in this fashion, the balance-rr
-mode allows individual connections between two hosts to effectively
-utilize greater than one interface's bandwidth.
-
-12.2.2 MT Link Monitoring for Multiple Switch Topology
-------------------------------------------------------
-
- Again, in actual practice, the MII monitor is most often used
-in this configuration, as performance is given preference over
-availability. The ARP monitor will function in this topology, but its
-advantages over the MII monitor are mitigated by the volume of probes
-needed as the number of systems involved grows (remember that each
-host in the network is configured with bonding).
-
-13. Switch Behavior Issues
-==========================
-
-13.1 Link Establishment and Failover Delays
--------------------------------------------
-
- Some switches exhibit undesirable behavior with regard to the
-timing of link up and down reporting by the switch.
-
- First, when a link comes up, some switches may indicate that
-the link is up (carrier available), but not pass traffic over the
-interface for some period of time. This delay is typically due to
-some type of autonegotiation or routing protocol, but may also occur
-during switch initialization (e.g., during recovery after a switch
-failure). If you find this to be a problem, specify an appropriate
-value to the updelay bonding module option to delay the use of the
-relevant interface(s).
-
- Second, some switches may "bounce" the link state one or more
-times while a link is changing state. This occurs most commonly while
-the switch is initializing. Again, an appropriate updelay value may
-help.
-
- Note that when a bonding interface has no active links, the
-driver will immediately reuse the first link that goes up, even if the
-updelay parameter has been specified (the updelay is ignored in this
-case). If there are slave interfaces waiting for the updelay timeout
-to expire, the interface that first went into that state will be
-immediately reused. This reduces down time of the network if the
-value of updelay has been overestimated, and since this occurs only in
-cases with no connectivity, there is no additional penalty for
-ignoring the updelay.
-
- In addition to the concerns about switch timings, if your
-switches take a long time to go into backup mode, it may be desirable
-to not activate a backup interface immediately after a link goes down.
-Failover may be delayed via the downdelay bonding module option.
-
-13.2 Duplicated Incoming Packets
---------------------------------
-
- NOTE: Starting with version 3.0.2, the bonding driver has logic to
-suppress duplicate packets, which should largely eliminate this problem.
-The following description is kept for reference.
-
- It is not uncommon to observe a short burst of duplicated
-traffic when the bonding device is first used, or after it has been
-idle for some period of time. This is most easily observed by issuing
-a "ping" to some other host on the network, and noticing that the
-output from ping flags duplicates (typically one per slave).
-
- For example, on a bond in active-backup mode with five slaves
-all connected to one switch, the output may appear as follows:
-
-# ping -n 10.0.4.2
-PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
-64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
-64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
-64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
-64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
-64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
-64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
-64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
-64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
-
- This is not due to an error in the bonding driver, rather, it
-is a side effect of how many switches update their MAC forwarding
-tables. Initially, the switch does not associate the MAC address in
-the packet with a particular switch port, and so it may send the
-traffic to all ports until its MAC forwarding table is updated. Since
-the interfaces attached to the bond may occupy multiple ports on a
-single switch, when the switch (temporarily) floods the traffic to all
-ports, the bond device receives multiple copies of the same packet
-(one per slave device).
-
- The duplicated packet behavior is switch dependent, some
-switches exhibit this, and some do not. On switches that display this
-behavior, it can be induced by clearing the MAC forwarding table (on
-most Cisco switches, the privileged command "clear mac address-table
-dynamic" will accomplish this).
-
-14. Hardware Specific Considerations
-====================================
-
- This section contains additional information for configuring
-bonding on specific hardware platforms, or for interfacing bonding
-with particular switches or other devices.
-
-14.1 IBM BladeCenter
---------------------
-
- This applies to the JS20 and similar systems.
-
- On the JS20 blades, the bonding driver supports only
-balance-rr, active-backup, balance-tlb and balance-alb modes. This is
-largely due to the network topology inside the BladeCenter, detailed
-below.
-
-JS20 network adapter information
---------------------------------
-
- All JS20s come with two Broadcom Gigabit Ethernet ports
-integrated on the planar (that's "motherboard" in IBM-speak). In the
-BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
-I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
-An add-on Broadcom daughter card can be installed on a JS20 to provide
-two more Gigabit Ethernet ports. These ports, eth2 and eth3, are
-wired to I/O Modules 3 and 4, respectively.
-
- Each I/O Module may contain either a switch or a passthrough
-module (which allows ports to be directly connected to an external
-switch). Some bonding modes require a specific BladeCenter internal
-network topology in order to function; these are detailed below.
-
- Additional BladeCenter-specific networking information can be
-found in two IBM Redbooks (www.ibm.com/redbooks):
-
-"IBM eServer BladeCenter Networking Options"
-"IBM eServer BladeCenter Layer 2-7 Network Switching"
-
-BladeCenter networking configuration
-------------------------------------
-
- Because a BladeCenter can be configured in a very large number
-of ways, this discussion will be confined to describing basic
-configurations.
-
- Normally, Ethernet Switch Modules (ESMs) are used in I/O
-modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
-JS20 will be connected to different internal switches (in the
-respective I/O modules).
-
- A passthrough module (OPM or CPM, optical or copper,
-passthrough module) connects the I/O module directly to an external
-switch. By using PMs in I/O module #1 and #2, the eth0 and eth1
-interfaces of a JS20 can be redirected to the outside world and
-connected to a common external switch.
-
- Depending upon the mix of ESMs and PMs, the network will
-appear to bonding as either a single switch topology (all PMs) or as a
-multiple switch topology (one or more ESMs, zero or more PMs). It is
-also possible to connect ESMs together, resulting in a configuration
-much like the example in "High Availability in a Multiple Switch
-Topology," above.
-
-Requirements for specific modes
--------------------------------
-
- The balance-rr mode requires the use of passthrough modules
-for devices in the bond, all connected to an common external switch.
-That switch must be configured for "etherchannel" or "trunking" on the
-appropriate ports, as is usual for balance-rr.
-
- The balance-alb and balance-tlb modes will function with
-either switch modules or passthrough modules (or a mix). The only
-specific requirement for these modes is that all network interfaces
-must be able to reach all destinations for traffic sent over the
-bonding device (i.e., the network must converge at some point outside
-the BladeCenter).
-
- The active-backup mode has no additional requirements.
-
-Link monitoring issues
-----------------------
-
- When an Ethernet Switch Module is in place, only the ARP
-monitor will reliably detect link loss to an external switch. This is
-nothing unusual, but examination of the BladeCenter cabinet would
-suggest that the "external" network ports are the ethernet ports for
-the system, when it fact there is a switch between these "external"
-ports and the devices on the JS20 system itself. The MII monitor is
-only able to detect link failures between the ESM and the JS20 system.
-
- When a passthrough module is in place, the MII monitor does
-detect failures to the "external" port, which is then directly
-connected to the JS20 system.
-
-Other concerns
---------------
-
- The Serial Over LAN (SoL) link is established over the primary
-ethernet (eth0) only, therefore, any loss of link to eth0 will result
-in losing your SoL connection. It will not fail over with other
-network traffic, as the SoL system is beyond the control of the
-bonding driver.
-
- It may be desirable to disable spanning tree on the switch
-(either the internal Ethernet Switch Module, or an external switch) to
-avoid fail-over delay issues when using bonding.
-
-
-15. Frequently Asked Questions
-==============================
-
-1. Is it SMP safe?
-
- Yes. The old 2.0.xx channel bonding patch was not SMP safe.
-The new driver was designed to be SMP safe from the start.
-
-2. What type of cards will work with it?
-
- Any Ethernet type cards (you can even mix cards - a Intel
-EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes,
-devices need not be of the same speed.
-
- Starting with version 3.2.1, bonding also supports Infiniband
-slaves in active-backup mode.
-
-3. How many bonding devices can I have?
-
- There is no limit.
-
-4. How many slaves can a bonding device have?
-
- This is limited only by the number of network interfaces Linux
-supports and/or the number of network cards you can place in your
-system.
-
-5. What happens when a slave link dies?
-
- If link monitoring is enabled, then the failing device will be
-disabled. The active-backup mode will fail over to a backup link, and
-other modes will ignore the failed link. The link will continue to be
-monitored, and should it recover, it will rejoin the bond (in whatever
-manner is appropriate for the mode). See the sections on High
-Availability and the documentation for each mode for additional
-information.
-
- Link monitoring can be enabled via either the miimon or
-arp_interval parameters (described in the module parameters section,
-above). In general, miimon monitors the carrier state as sensed by
-the underlying network device, and the arp monitor (arp_interval)
-monitors connectivity to another host on the local network.
-
- If no link monitoring is configured, the bonding driver will
-be unable to detect link failures, and will assume that all links are
-always available. This will likely result in lost packets, and a
-resulting degradation of performance. The precise performance loss
-depends upon the bonding mode and network configuration.
-
-6. Can bonding be used for High Availability?
-
- Yes. See the section on High Availability for details.
-
-7. Which switches/systems does it work with?
-
- The full answer to this depends upon the desired mode.
-
- In the basic balance modes (balance-rr and balance-xor), it
-works with any system that supports etherchannel (also called
-trunking). Most managed switches currently available have such
-support, and many unmanaged switches as well.
-
- The advanced balance modes (balance-tlb and balance-alb) do
-not have special switch requirements, but do need device drivers that
-support specific features (described in the appropriate section under
-module parameters, above).
-
- In 802.3ad mode, it works with systems that support IEEE
-802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
-switches currently available support 802.3ad.
-
- The active-backup mode should work with any Layer-II switch.
-
-8. Where does a bonding device get its MAC address from?
-
- When using slave devices that have fixed MAC addresses, or when
-the fail_over_mac option is enabled, the bonding device's MAC address is
-the MAC address of the active slave.
-
- For other configurations, if not explicitly configured (with
-ifconfig or ip link), the MAC address of the bonding device is taken from
-its first slave device. This MAC address is then passed to all following
-slaves and remains persistent (even if the first slave is removed) until
-the bonding device is brought down or reconfigured.
-
- If you wish to change the MAC address, you can set it with
-ifconfig or ip link:
-
-# ifconfig bond0 hw ether 00:11:22:33:44:55
-
-# ip link set bond0 address 66:77:88:99:aa:bb
-
- The MAC address can be also changed by bringing down/up the
-device and then changing its slaves (or their order):
-
-# ifconfig bond0 down ; modprobe -r bonding
-# ifconfig bond0 .... up
-# ifenslave bond0 eth...
-
- This method will automatically take the address from the next
-slave that is added.
-
- To restore your slaves' MAC addresses, you need to detach them
-from the bond (`ifenslave -d bond0 eth0'). The bonding driver will
-then restore the MAC addresses that the slaves had before they were
-enslaved.
-
-16. Resources and Links
-=======================
-
- The latest version of the bonding driver can be found in the latest
-version of the linux kernel, found on http://kernel.org
-
- The latest version of this document can be found in the latest kernel
-source (named Documentation/networking/bonding.txt).
-
- Discussions regarding the usage of the bonding driver take place on the
-bonding-devel mailing list, hosted at sourceforge.net. If you have questions or
-problems, post them to the list. The list address is:
-
-bonding-devel@lists.sourceforge.net
-
- The administrative interface (to subscribe or unsubscribe) can
-be found at:
-
-https://lists.sourceforge.net/lists/listinfo/bonding-devel
-
- Discussions regarding the developpement of the bonding driver take place
-on the main Linux network mailing list, hosted at vger.kernel.org. The list
-address is:
-
-netdev@vger.kernel.org
-
- The administrative interface (to subscribe or unsubscribe) can
-be found at:
-
-http://vger.kernel.org/vger-lists.html#netdev
-
-Donald Becker's Ethernet Drivers and diag programs may be found at :
- - http://web.archive.org/web/*/http://www.scyld.com/network/
-
-You will also find a lot of information regarding Ethernet, NWay, MII,
-etc. at www.scyld.com.
-
--- END --