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cable helper-address
The cable helper-address command, as is the case with the ip helper-address command, cannot be used
on slave interfaces, so these commands are automatically removed from an interface configuration when
the interface is configured as a slave interface. Slave interfaces use the IP configuration of the master
interface, which includes not only the IP address for the interface itself, but also the helper addresses
that have been configured on the master interface.
You can repeat this command to specify any number of helper addresses, but the Cisco IOS software uses
Tip
only the first 16 valid addresses that are configured on each interface (using either the cable helper-
address command or the ip helper-address command) when forwarding DHCP requests.
Examples
The following example shows how to forward UDP broadcasts from both CMs and CPE devices to the
DHCP server at 172.23.66.44:
Router(config)# interface cable 1/0
Router(config-if)# cable helper-address 172.23.66.44
Router(config-if)# exit
Router(config)#
The following example shows how to forward UDP broadcasts from CMs and CPE devices to separate
DHCP servers:
Router(config)# interface cable 6/0
Router(config-if)# cable helper-address 172.23.66.143 host
Router(config-if)# cable helper-address 172.23.66.144 cable-modem
Router(config-if)# exit
Router(config)#
The following example shows that when you specify the cable-modem and host options with the same
IP address, the second command overwrites the first one:
Router(config)# interface cable 3/0
Router(config-if)# cable helper-address 10.10.10.13 host
Router(config-if)# cable helper-address 10.10.10.13 cable-modem
Router(config-if)# exit
Router(config)# exit
Router# show running-config | include helper-address
cable helper-address 10.10.10.13 cable-modem
Router#
Related Commands
Command
cable dhcp-giaddr
cable relay-agent-option
cable source-verify
cable telco-return spd dhcp-
authenticate
Cisco Broadband Cable Command Reference Guide
2-110
Description
Modifies the GIADDR field of DHCPDISCOVER and
DHCPREQUEST packets with a Relay IP address before they are
forwarded to the DHCP server.
Enables the system to insert the CM MAC address into a DHCP
packet received from a CM or host and forward the packet to a DHCP
server.
Turns on CM upstream verification.
Enforces the telco-return CM to use a specific Dynamic Host
Configuration Protocol (DHCP) server.
Chapter 2
Cisco CMTS Configuration Commands
OL-1581-08
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