Configuring a Dynamic Host Configuration Protocol (DHCP) server

Clients not being configured with all options

If a client has been configured with an IP address and DHCP options, but not with all the options you specified in the DHCP Server Manager, too many options may have been specified for the client. The DHCP server has a 274-byte practical limit for DHCP options (466 bytes if the Option Overload feature is enabled). Check /usr/adm/syslog for one or more messages of the form ``Option code did not fit in packet''. This indicates that the DHCP server did not send all the options specified for the client because the total size of all the client's options exceeded the ``options'' field size.

Follow the steps below to determine why there may be too many options:

  1. Check to see if the option overload parameter is specified in the DHCP server parameters. Setting this parameter allows the server to use the ``sname'' and ``file'' fields of the ``offer'' message, which provides an additional 192 bytes for options. See ``Specifying DHCP server parameters''.

  2. Check the values configured for the options sent to the client in the appropriate DHCP option list (subnet, client, user class, vendor class or global). You can specify an array of values for some options, such as an array of IP addresses for the Routers option. Arrays that consist of many nonsequential values consume space in the ``options'' field which excludes options found farther down on the configured list from being sent in the ``offer'' message. For arrays of IP addresses, a single range of addresses consumes the least space.

  3. Determine if the client included a ``parameter request list'' in the ``discover'' message by examining the client's DHCP configuration. These options take precedence over the options you have configured for the client, subnet and classes in the DHCP Server Manager. If the options requested by the client are different from the options configured by you, the total group of options may exceed the size limitation. Depending upon the total size of all the configured options, the options you've configured which are toward the bottom of the list may be excluded from the ``offer'' message sent to the client. If this scenario is true, you will have to select the most important options for the client and eliminate the less important ones.

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SCO OpenServer Release 5.0.7 -- 11 February 2003