Cisco Broadband Cable Command Reference Guide

Chapter 2 Cisco Cable Modem Termination System Commands
cable helper-address
Syntax Description
OL-1581-05
Cisco Broadband Cable Command Reference Guide
cable helper-address
To specify a destination IP address for User Datagram Protocol (UDP) broadcast Dynamic Host
Configuration Protocol (DHCP) packets, use the cable helper-address command in cable interface or
subinterface configuration mode. To disable this feature, use the no form of this command.
cable helper-address IP-address [cable-modem | host]
no cable helper-address IP-address [cable-modem | host]
Note You must specify both the cable-modem or host options in separate commands if you decide to use
them. If you specify only one option, then the other type of device (cable modem or host) will not be
able to connect with a DHCP server.
Defaults If no options are specified, both CM and host UDP broadcasts are forwarded.
Command Modes Interface and subinterface configuration (cable interface only)
Command History
IP-address The IP address of a DHCP server to which UDP broadcast packets will
be sent.
cable-modem (Optional) Specifies that only CM UDP broadcasts are forwarded.
host (Optional) Specifies that only host UDP broadcasts are forwarded.
Release Modification
12.1 T This command was introduced.
12.1(3a)EC The subinterface support was added.
Usage Guidelines This commands allows the use of separate DHCP servers for hosts and CMs. The cable-modem keyword
specifies that only UDP broadcasts from CMs are forwarded to that particular destination IP address.
The host keyword specifies that only UDP broadcasts from hosts (CPE devices) are forwarded to that
particular destination IP address.
Note Cisco IOS software provides similar functionality with the ip helper-address command, but do not use
the ip helper-address command on cable interfaces. The cable helper-address command is optimized
for cable interfaces and DOCSIS networks and should be used on cable interfaces instead of the ip
helper-address command.
2-73