Cisco Systems uBR7200 Activating DHCP giaddr, Verifying DHCP giaddr Activation, MC-577, Command

Configuring Headend Broadband Access Router Features

Configuring DHCP Options

With the cable relay agent activated, the Cisco uBR7200 series will insert the cable modem MAC address into a DHCP packet when a packet is received from a cable modem or another host. The Cisco uBR7200 series will then forward the packet to a DHCP server.

To activate the cable relay agent, use the following command in cable interface configuration mode:

Command	Purpose
CMTS01(config-if)#cable relay-agent-option	Activates the cable relay agent. This is the default.

Troubleshooting Tips

To troubleshoot the configuration, perform the following tasks:

•Make sure you entered the correct port and cable modem card slot number when you activated cable relay-agent-option.

•A DOCSIS-based DHCP server is required. The DHCP server verifies that the “fixed” IP address, if any, returned to the host is valid for the IP subnet on that downstream interface. The IP address must be unique and valid in the subnet for the end user to obtain connectivity.

Activating DHCP giaddr

Configure the Cisco uBR7200 series so it will either assign primary addresses to both cable modems and remote hosts, or assign primary addresses to cable modems and secondary addresses to remote hosts.

To configure cable DHCP giaddr functionality, use one of the following commands in cable interface configuration mode:

Command	Purpose
CMTS01(config-if)#cable dhcp-giaddr primary	Enables cable DHCP giaddr functionality so that primary
or	addresses are assigned to both cable modems and remote
	hosts.
CMTS01(config-if)#cable dhcp-giaddr policy	Enables cable DHCP giaddr functionality so that primary
	addresses are assigned to cable modems and secondary
	addresses are assigned to remote hosts.

To disable cable DHCP giaddr functionality (the default) after it has been enabled, enter the no cable dhcp-giaddrcommand in cable interface configuration mode.

Verifying DHCP giaddr Activation

To verify whether DHCP giaddr has been activated, enter the show running-configcommand and look for the cable interface configuration information. If DHCP giaddr has been activated, a notation will appear in this output. If DHCP giaddr has been deactivated, it will not appear in the output.

Cisco IOS Multiservice Applications Configuration Guide

MC-577