Solaris DHCP Administration Guide

DHCP Option Information

Historically, DHCP option information has been stored in several places in Solaris DHCP, including the server's dhcptab table, the client's dhcptags file, and internal tables of in.dhcpd, snoop, dhcpinfo, and dhcpmgr. In an effort to consolidate option information, the Solaris 8 DHCP product introduced the /etc/dhcp/inittab file. See the dhcp_inittab man page for detailed information about the file.

The Solaris DHCP client uses the DHCP inittab file as a replacement for the dhcptags file to obtain information about option codes received in its DHCP packet. The in.dhcpd, snoop, and dhcpmgr programs on the DHCP server use the inittab file as well.

Note –

Most sites that use Solaris DHCP are not affected by this change. Your site is affected only if you plan to upgrade to Solaris 8, you previously created new DHCP options and modified the /etc/dhcp/dhcptags file, and you want to retain the changes. When you upgrade, the upgrade log notifies you that your dhcptags file had been modified and that you should make changes to the DHCP inittab file.

Differences Between dhcptags and inittab

The inittab file contains more information than the dhcptags file and it uses a different syntax.

A sample dhcptags entry is:

33 StaticRt - IPList Static_Routes

where 33 is the numeric code that is passed in the DHCP packet, StaticRt is the option name, IPList indicates the expected data is a list of IP addresses, and Static_Routes is a more descriptive name.

The inittab file consists of one-line records that describe each option. The format is similar to the format that defines symbols in dhcptab. The following table describes the syntax of the inittab.

Table 6–3 DHCP inittab File Syntax




Name of the option. The option name must be unique within its option category, and not overlap with other option names in the Standard, Site, and Vendor categories. For example, you cannot have two Site options with the same name, and you should not create a Site option with the same name as a Standard option.  


Identifies the namespace in which the option belongs. Must be one of Standard, Site, Vendor, Field, or Internal. 


Identifies the option when it is sent over the network. In most cases, the code uniquely identifies the option, without a category. However, in the case of internal categories like Field or Internal, a code might be used for other purposes and thus might not be globally unique. The code should be unique within the option's category, and not overlap with codes in the Standard and Site fields.  


Describes the data associated with this option. Valid types are IP, Ascii, Octet, Boolean, Unumber8, Unumber16, Unumber32, Unumber64, Snumber8, Snumber16, Snumber32, and Snumber64. For numbers, an initial U or S indicates that the number is unsigned or signed, and the digits at the end indicate the amount of bits in the number. The type is not case sensitive. 


Describes how many units of data make up a whole value for this option.  


Describes how many whole values are allowed for this option. 0 indicates an infinite number. 


Describes which programs can use this information. This should be set to sdmi, where:

    s – snoop

    d – in.dhcpd

    m – dhcpmgr

    i – dhcpinfo

A sample inittab entry is:

StaticRt Standard, 33, IP, 2, 0, sdmi

This entry describes an option named StaticRt, which is in the Standard category and is option code 33. The expected data is a potentially infinite number of pairs of IP addresses because the type is IP, granularity is 2, and maximum is infinite (0). The consumers of this option are sdmi: snoop, in.dhcpd, dhcpmgr, and dhcpinfo.

Converting dhcptags Entries to inittab Entries

If you previously added entries to your dhcptags file, you must add corresponding entries to the new inittab file. The following example shows how a sample dhcptags entry might be expressed in inittab format.

Suppose you had added the following dhcptags entry for fax machines connected to the network:

128 FaxMchn - IP Fax_Machine

The code 128 means that it must be in the site category, the option name is FaxMchn, the data type is IP.

The corresponding inittab entry might be:

FaxMchn SITE, 128, IP, 1, 1, sdmi

The granularity of 1 and maximum of 1 indicate that one IP address is expected for this option.