user manual

Configuring Headend Broadband Access Router Features
Configuring DHCP Options
MC-577
Cisco IOS Multiservice Applications Configuration Guide
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:
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:
To disable cable DHCP giaddr functionality (the default) after it has been enabled, enter the no cable
dhcp-giaddr command in cable interface configuration mode.
Verifying DHCP giaddr Activation
To verify whether DHCP giaddr has been activated, enter the show running-config command 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.
Command Purpose
CMTS01(config-if)# cable relay-agent-option
Activates the cable relay agent. This is the default.
Command Purpose
CMTS01(config-if)# cable dhcp-giaddr primary
or
CMTS01(config-if)# cable dhcp-giaddr policy
Enables cable DHCP giaddr functionality so that primary
addresses are assigned to both cable modems and remote
hosts.
Enables cable DHCP giaddr functionality so that primary
addresses are assigned to cable modems and secondary
addresses are assigned to remote hosts.