Cisco 2950 Software Configuration Guide - Page 432
Setting the Snooping Method
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Configuring IGMP Snooping Chapter 21 Configuring IGMP Snooping and MVR Setting the Snooping Method Multicast-capable router ports are added to the forwarding table for every Layer 2 multicast entry. The switch learns of such ports through one of these methods: • Snooping on IGMP queries, Protocol Independent Multicast (PIM) packets, and Distance Vector Multicast Routing Protocol (DVMRP) packets • Listening to Cisco Group Management Protocol (CGMP) packets from other routers • Statically connecting to a multicast router port with the ip igmp snooping mrouter global configuration command You can configure the switch either to snoop on IGMP queries and PIM/DVMRP packets or to listen to CGMP self-join or proxy-join packets. By default, the switch snoops on PIM/DVMRP packets on all VLANs. To learn of multicast router ports through only CGMP packets, use the ip igmp snooping vlan vlan-id mrouter learn cgmp global configuration command. When this command is entered, the router listens to only CGMP self-join and CGMP proxy-join packets and no other CGMP packets. To learn of multicast router ports through only PIM-DVMRP packets, use the ip igmp snooping vlan vlan-id mrouter learn pim-dvmrp global configuration command. Beginning in privileged EXEC mode, follow these steps to alter the method in which a VLAN interface dynamically accesses a multicast router: Step 1 Step 2 Command configure terminal ip igmp snooping vlan vlan-id mrouter learn {cgmp | pim-dvmrp} Step 3 Step 4 Step 5 end show ip igmp snooping copy running-config startup-config Purpose Enter global configuration mode. Enable IGMP snooping on a VLAN.The VLAN ID range is 1 to 1005 when the standard software image (SI) is installed and 1 to 4094 when the enhanced software image (EI) is installed. Specify the multicast router learning method: • cgmp-Listen for CGMP packets. This method is useful for reducing control traffic. • pim-dvmrp-Snoop on IGMP queries and PIM-DVMRP packets. This is the default. Return to privileged EXEC mode. Verify the configuration. (Optional) Save your entries in the configuration file. This example shows how to configure IGMP snooping to use CGMP packets as the learning method: Switch# configure terminal Switch(config)# ip igmp snooping vlan 1 mrouter learn cgmp Switch(config)# end Switch# show ip igmp snooping vlan 1 Global IGMP Snooping configuration: IGMP snooping :Enabled IGMPv3 snooping (minimal) :Enabled Report suppression :Enabled TCN solicit query :Disabled TCN flood query count :2 21-8 Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide 78-11380-10
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