System information

BSR 64000 Configuration and Management Guide
6-4
Configuring the Cable Helper and IP Helper Addresses
The cable helper IP address function disassembles a CM DHCP broadcast packet, and
reassembles it into a unicast packet so that the packet can traverse the router and
communicate with the DHCP server.
The cable helper address function is used in conjunction with the DHCP relay
function. If the ip dhcp relay information option command is not set, all requests
are sent to the IP address defined by the ip helper-address command. When ip dhcp
relay information option is enabled, the BSR can distinguish between requests from
CMs, secondary hosts and secondary MTAs, and forwards the DHCP requests to the
cable helper IP address specifically defined for the requesting device.
Follow the steps in this section to configure the cable helper and IP helper address:
1. Issue the cable helper-address cable-modem command in Interface
Configuration mode to configure the helper IP address for the cable interface to
forward only DHCP broadcasts, as shown below:
MOT(config-if)#cable helper-address <A.B.C.D> cable-modem
where:
A.B.C.D is the IP address of the destination DHCP server.
2. Optionally use the cable helper-address host command in Interface
Configuration mode to configure a secondary helper IP address for the CPE to
forward only UDP broadcasts, as shown below:
MOT(config-if)#cable helper-address <A.B.C.D> host
where:
A.B.C.D is the IP address of the destination DHCP server.
Note: Multiple cable-helper addresses can be configured for CMs, hosts, and
MTAs. If you want both CM and host DHCP requests to be sent to the same
DHCP server, configure the same cable helper IP address for hosts and CMs.