Relaying DHCP Packets That Originate from a Cable Modem

You can use the DHCP vendor class identifier option (option 60) to configure DHCP relay to relay DHCP packets that originate from a cable modem to an external DHCP server that provides the cable modem with the configuration it requests.

Configure the vendor class identifier option to match the string used by cable modems—DHCP relay then forwards the packets to each DHCP server that you configured with the set dhcp vendor-option command (these servers are also considered to be cable-modem DHCP servers).

• To relay DHCP packets from a cable modem:
  host1(config)#set dhcp relay host1(config)#service dhcp-local equal-access host1(config)#set dhcp vendor-option equals docsis relay 192.168.1.1 host1(config)#set dhcp vendor-option equals cablemodem relay 192.168.1.1

  Use the show dhcp summary and show dhcp vendor-option commands to display information about the cable modem DHCP relay configuration. See the Monitoring and Troubleshooting DHCP chapter in this guide.