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Cisco uBR10012 Universal Broadband Router Software Configuration Guide
OL-1520-05
Chapter3 Configuring Cable Interface Features for the CiscouBR10012Router Configuring Optional Cable Interface Features
Access Lists and the cable ip-multicast echo Command
The cable ip-multicast-echo command is enabled by default on the Cisco uBR10012 router, so that
multicast IP packets that arrive on the upstream at the Cisco CMTS are forwarded on the appropriate
downstream ports so that they are delivered to the other CMs and CPE devices on that segment of the
network. This allows the cable network to behave like a standard Ethernet network in terms of its
handling of multicast IP traffic.
However, on the Cisco uBR10012 router, input access lists are not applied to the multicast traffic that is
echoed on each downstream. To control the echoed multicast traffic, you therefore need to configure an
output access list and apply it to each downstream interface.
Refer to the Cisco Broadband Cable Command Reference Guide on Cisco.com for additional
information on access lists and multicast echo:
http://www.cisco.com/univercd/cc/td/doc/product/cable/bbccmref/index.htm
Setting IP Broadcast Echo
By default, the CiscouBR10012router does not echo IP broadcast packets. To activate IP broadcast
echo, use the following command in cable interface configuration mode.
To disable IP broadcast echo when it is enabled, enter the no cable ip-broadcast-echo command in cable
interface configuration mode.
Verifying IP Broadcast Echo
To determine whether IP broadcast echo is activated or deactivated, enter the
moresystem:running-config command and look for a notation in the cable interface configuration
information:
Router# more system:running-config
Building configuration...
Current configuration:
!
interface cable5/0/0
ip address 1.1.1.1 255.255.255.0
no keepalive
cable ip-broadcast-echo
cable downstream annex B
cable downstream modulation 64qam
cable downstream interleave-depth 32
cable upstream 0 frequency 15008000
no cable upstream 0 shutdown
Command Purpose
Router(config-if)# cable ip-broadcast-echo Enables IP broadcast echo.