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Chapter 2
Cisco CMTS Configuration Commands
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.
Syntax Description
IP-address
cable-modem
host
You must specify both the cable-modem or host options in separate commands, using separate IP
Note
addresses, 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. In addition, if you use the cable-modem
or host option with the same IP address that was previously configured with this command, the new
configuration overwrites the old configuration.
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
Release
12.1 T
12.1(3a)EC
Usage Guidelines
This command enables CMs and their attached CPE devices (hosts) to use separate DHCP servers, so
that CMs and hosts receive their IP addresses from separate address pools. The cable-modem keyword
specifies that only UDP DHCP 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.
The cable helper-address command is similar to the ip helper-address command, but the cable helper-
address command has been enhanced for cable interfaces and DOCSIS networks to allow separate
helper addresses for CMs and hosts. Use only the cable helper-address command on cable interfaces,
and use the ip helper-address command on all non-cable interfaces.
OL-1581-08
cable helper-address IP-address [cable-modem | host]
no cable helper-address IP-address [cable-modem | host]
Modification
This command was introduced.
The subinterface support was added.
The IP address of a DHCP server to which UDP broadcast packets will
be sent.
(Optional) Specifies that only CM UDP broadcasts are forwarded.
(Optional) Specifies that only host UDP broadcasts are forwarded.
Cisco Broadband Cable Command Reference Guide
cable helper-address
2-109
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