Enabling Cgmp Server Support - Cisco Catalyst 3550 series Software Configuration Manual

Configuring Optional Multicast Routing Features

Enabling CGMP Server Support

The multilayer switch serves as a CGMP server for devices that do not support IGMP snooping but have
CGMP client functionality. CGMP is a protocol used on Cisco routers and multilayer switches connected
to Layer 2 Catalyst switches to perform tasks similar to those performed by IGMP. CGMP is necessary
because the Layer 2 switch cannot distinguish between IP multicast data packets and IGMP report
messages, which are both at the MAC-level and are addressed to the same group address.
Beginning in privileged EXEC mode, follow these steps to enable the CGMP server on the multilayer
switch interface:
Command
Step 1
configure terminal
Step 2 interface interface-id
Step 3 ip cgmp [proxy]
Step 4 end
Step 5
show running-config
Step 6
copy running-config startup-config
Step 7
To disable CGMP on the interface, use the no ip cgmp interface configuration command.
When multiple Cisco CGMP-capable devices are connected to a switched network and the ip cgmp
proxy command is needed, we recommend that all devices be configured with the same CGMP option
and have precedence for becoming the IGMP querier over non-Cisco routers.
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Purpose
Enter global configuration mode.
Enter interface configuration mode, and specify the interface that is
connected to the Layer 2 Catalyst switch.
Enable CGMP on the interface.
By default, CGMP is disabled on all interfaces.
Enabling CGMP triggers a CGMP join message. Enable CGMP only on
Layer 3 interfaces connected to Layer 2 Catalyst switches.
(Optional) When you enter the proxy keyword, the CGMP proxy function
is enabled. The proxy router advertises the existence of
non-CGMP-capable routers by sending a CGMP join message with the
non-CGMP-capable router MAC address and a group address
of 0000.0000.0000.
To perform CGMP proxy, the multilayer switch must be the IGMP
Note
querier. If you configure the ip cgmp proxy command, you must
manipulate the IP addresses so that the switch is the IGMP
querier, which might be the highest or lowest IP address,
depending on which version of IGMP is running on the network.
An IGMP Version 2 querier is selected based on the lowest IP
address on the interface. An IGMP Version 1 querier is selected
based on the multicast routing protocol used on the interface.
Return to privileged EXEC mode.
Verify your entries.
(Optional) Save your entries in the configuration file.
Verify the Layer 2 Catalyst switch CGMP-client configuration. For more
information, refer to the documentation that shipped with the product.
Chapter 34 Configuring IP Multicast Routing
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