Selecting DHCP Parameters

The SAE sends a set of parameters to the DHCP server in the JunosE router. The DHCP server determines the IP address offered, as well as the options sent to the DHCP client. The parameters comprise IP address authorization parameters, as well as parameters stored in a DHCP profile. Parameters in the DHCP profile override authorization parameters.

Note: JunosE routers do not currently support the functionality described in this section. DHCP options and BOOTP options that the SAE sends to the JunosE router are ignored.

DHCP servers use DHCP options to configure DHCP clients. The DHCP local server in the JunosE router supports a subset of DHCP options. The SAE supports all DHCP options defined in RFC 2132—DHCP Options and BOOTP Vendor Extensions (March 1997) by name. It also supports other options, but you need to specify them by number and type. The DHCP options allow a flexible definition of parameters offered to DHCP subscribers. For example, they allow integration with cable modems or set-top boxes because you can configure options to control the boot sequence of these devices.

You can configure DHCP options in DHCP profiles and in DHCP classification scripts. DHCP Options Supported on the SAE lists the name, number, and type of all supported DHCP options. You can use these fields to configure DHCP options.

The following example shows how to specify an option by number and by type. The two statements identify the same option:

dhcp[12]dhcp['host-name']

In SDX software earlier than Release 4.2, you had to include the option type in your option definition. For example:

dhcp[12].string = HOST

You can now write:

dhcp[12] = HOST

Note that the earlier method of defining options still works in Release 4.2 and later.

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