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diff --git a/docs/textdocs/DHCP-Server-Configuration.txt b/docs/textdocs/DHCP-Server-Configuration.txt new file mode 100644 index 00000000000..499706955fb --- /dev/null +++ b/docs/textdocs/DHCP-Server-Configuration.txt @@ -0,0 +1,240 @@ +Subject: DHCP Server Configuration for SMB Clients +Date: March 1, 1998 +Updated: May 15, 2001 +Contributor: John H Terpstra <jht@samba.org> +Support: This is an unsupported document. Refer to documentation that is + supplied with the ISC DHCP Server. Do NOT email the contributor + for ANY assistance. +=============================================================================== + +Background: +=========== + +We wish to help those folks who wish to use the ISC DHCP Server and provide +sample configuration settings. Most operating systems today come ship with +the ISC DHCP Server. ISC DHCP is available from: + ftp://ftp.isc.org/isc/dhcp + +Incorrect configuration of MS Windows clients (Windows9X, Windows ME, Windows +NT/2000) will lead to problems with browsing and with general network +operation. Windows 9X/ME users often report problems where the TCP/IP and related +network settings will inadvertantly become reset at machine start-up resulting +in loss of configuration settings. This results in increased maintenance +overheads as well as serious user frustration. + +In recent times users on one mailing list incorrectly attributed the cause of +network operating problems to incorrect configuration of Samba. + +One user insisted that the only way to provent Windows95 from periodically +performing a full system reset and hardware detection process on start-up was +to install the NetBEUI protocol in addition to TCP/IP. This assertion is not +correct. + +In the first place, there is NO need for NetBEUI. All Microsoft Windows clients +natively run NetBIOS over TCP/IP, and that is the only protocol that is +recognised by Samba. Installation of NetBEUI and/or NetBIOS over IPX will +cause problems with browse list operation on most networks. Even Windows NT +networks experience these problems when incorrectly configured Windows95 +systems share the same name space. It is important that only those protocols +that are strictly needed for site specific reasons should EVER be installed. + +Secondly, and totally against common opinion, DHCP is NOT an evil design but is +an extension of the BOOTP protocol that has been in use in Unix environments +for many years without any of the melt-down problems that some sensationalists +would have us believe can be experienced with DHCP. In fact, DHCP in covered by +rfc1541 and is a very safe method of keeping an MS Windows desktop environment +under control and for ensuring stable network operation. + +Please note that MS Windows systems as of MS Windows NT 3.1 and MS Windows 95 +store all network configuration settings a registry. There are a few reports +from MS Windows network administrators that warrant mention here. It would appear +that when one sets certain MS TCP/IP protocol settings (either directly or via +DHCP) that these do get written to the registry. Even though a subsequent +change of setting may occur the old value may persist in the registry. This +has been known to create serious networking problems. + +An example of this occurs when a manual TCP/IP environment is configured to +include a NetBIOS Scope. In this event, when the administrator then changes the +configuration of the MS TCP/IP protocol stack, without first deleting the +current settings, by simply checking the box to configure the MS TCP/IP stack +via DHCP then the NetBIOS Scope that is still persistent in the registry WILL be +applied to the resulting DHCP offered settings UNLESS the DHCP server also sets +a NetBIOS Scope. It may therefore be prudent to forcibly apply a NULL NetBIOS +Scope from your DHCP server. The can be done in the dhcpd.conf file with the +parameter: + option netbios-scope ""; + +While it is true that the Microsoft DHCP server that comes with Windows NT +Server provides only a sub-set of rfc1533 functionality this is hardly an issue +in those sites that already have a large investment and commitment to Unix +systems and technologies. The current state of the art of the DHCP Server +specification in covered in rfc2132. + +This document aims to provide enough background information so that the +majority of site can without too much hardship get the Internet Software +Consortium's (ISC) DHCP Server into operation. The key benefits of using DHCP +includes: + +1) Automated IP Address space management and maximised re-use of available IP +Addresses, + +2) Automated control of MS Windows client TCP/IP network configuration, + +3) Automatic recovery from start-up and run-time problems with Windows95. + + + +Client Configuration for SMB Networking: +======================================== +SMB network clients need to be configured so that all standard TCP/IP name to +address resolution works correctly. Once this has been achieved the SMB +environment provides additional tools and services that act as helper agents in +the translation of SMB (NetBIOS) names to their appropriate IP Addresses. One +such helper agent is the NetBIOS Name Server (NBNS) or as Microsoft called it +in their Windows NT Server implementation WINS (Windows Internet Name Server). + +A client needs to be configured so that it has a unique Machine (Computer) +Name. + +This can be done, but needs a few NT registry hacks and you need to be able to +speak UNICODE, which is of course no problem for a True Wizzard(tm) :) +Instructions on how to do this (including a small util for less capable +Wizzards) can be found at + + http://www.unixtools.org/~nneul/sw/nt/dhcp-netbios-hostname.html + + +All remaining TCP/IP networking parameters can be assigned via DHCP. These include: + +a) IP Address, +b) Netmask, +c) Gateway (Router) Address, +d) DNS Domain Name, +e) DNS Server addresses, +f) WINS (NBNS) Server addresses, +g) IP Forwarding, +h) Timezone offset, +i) Node Type, +j) NetBIOS Scope + +Other assignments can be made from a DHCP server too, but the above cover the +major needs. + +Note: IF ever an entry has has been made to the NetBIOS Scope field of the +TCP/IP configuration panel on an MS Windows machine, and it has then been +committed, then that setting may become persistent. In such a c ase it is better +to configure the DHCP server with a NetBIOS Scope consisting of an empty string +(ie: A NULL scope). + + +DHCP Server Installation: +========================= +It is assumed that you will have obtained a copy of the GPL'd ISC DHCP server +source files from ftp://ftp.isc.org/isc/dhcp, it is also assumed that you have +compiled the sources and have installed the binary files. + +The following simply serves to provide sample configuration files to enable +dhcpd to operate. The sample files assume that your site is configured to use +private IP network address space using the Class B range of 172.16.1.0 - +172.16.1.255 and is using a netmask of 255.255.255.0 (ie:24 bits). It is +assumed that your router to the outside world is at 172.16.1.254 and that your +Internet Domain Name is bestnet.com.au. The IP Address range 172.16.1.100 to +172.16.1.240 has been set aside as your dynamically allocated range. In +addition, bestnet.com.au have two print servers that need to obtain settings +via BOOTP. The machine linux.bestnet.com.au has IP address 172.16.1.1 and is +you primary Samba server with WINS support enabled by adding the parameter to +the /etc/smb.conf file: [globals] wins support = yes. The dhcp lease time will +be set to 20 hours. + +Configuration Files: +==================== +Before dhcpd will run you need to install a file that speifies the +configuration settings, and another that holds the database of issued IP +addresses. On many systems these are stored in the /etc directory on the Unix +system. + +Example /etc/dhcpd.conf: +======================== +server-identifier linux.bestnet.com.au; + +subnet 172.16.1.0 netmask 255.255.255.0 { + range 172.16.1.100 172.16.1.240; + default-lease-time 72000; + max-lease-time 144000; + option subnet-mask 255.255.255.0; + option broadcast-address 172.16.1.255; + option routers 172.16.1.254; + option domain-name-servers 172.16.1.1, 172.16.1.2; + option domain-name "bestnet.com.au"; + option time-offset 39600; + option ip-forwarding off; + option netbios-name-servers 172.16.0.1, 172.16.0.1; + option netbios-dd-server 172.16.0.1; + option netbios-node-type 8; + option netbios-scope ""; +} + +; Note: The above netbios-scope is purposely an empty (NULL) string. + +group { + next-server 172.16.1.10; + option subnet-mask 255.255.255.0; + option domain-name "bestnet.com.au"; + option domain-name-servers 172.16.1.1, 172.16.0.2; + option netbios-name-servers 172.16.0.1, 172.16.0.1; + option netbios-dd-server 172.16.0.1; + option netbios-node-type 8; + option netbios-scope "SomeCrazyScope"; + option routers 172.16.1.240; + option time-offset 39600; + host lexmark1 { + hardware ethernet 06:07:08:09:0a:0b; + fixed-address 172.16.1.245; + } + host epson4 { + hardware ethernet 01:02:03:04:05:06; + fixed-address 172.16.1.242; + } +} + + +Creating the /etc/dhcpd.leases file: +==================================== +At a Unix shell create an empty dhcpd.leases file in the /etc directory. +You can do this by typing: cp /dev/null /etc/dhcpd.leases + + +Setting up a route table for all-ones addresses: +================================================ +Quoting from the README file that comes with the ISC DHCPD Server: + + BROADCAST + +In order for dhcpd to work correctly with picky DHCP clients (e.g., +Windows 95), it must be able to send packets with an IP destination +address of 255.255.255.255. Unfortunately, Linux insists on changing +255.255.255.255 into the local subnet broadcast address (here, that's +192.5.5.223). This results in a DHCP protocol violation, and while +many DHCP clients don't notice the problem, some (e.g., all Microsoft +DHCP clients) do. Clients that have this problem will appear not to +see DHCPOFFER messages from the server. + +It is possible to work around this problem on some versions of Linux +by creating a host route from your network interface address to +255.255.255.255. The command you need to use to do this on Linux +varies from version to version. The easiest version is: + + route add -host 255.255.255.255 dev eth0 + +On some older Linux systems, you will get an error if you try to do +this. On those systems, try adding the following entry to your +/etc/hosts file: + +255.255.255.255 all-ones + +Then, try: + + route add -host all-ones dev eth0 + + +For more information please refer to the ISC DHCPD Server documentation. |