Netgear XCM8806 Chassis User Manual - Page 734
Static IGMP, On NETGEAR
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NETGEAR 8800 User Manual enable igmp snooping {forward-mcrouter-only | {vlan} | with-proxy vr } disable igmp snooping {forward-mcrouter-only | with-proxy | vlan } When a port sends an IGMP leave message, the switch removes the IGMP snooping entry after 1000 milliseconds (the leave time is configurable, ranging from 0 to 10000 ms). The switch sends a query to determine which ports want to remain in the multicast group. If other members of the VLAN want to remain in the multicast group, the switch ignores the leave message, but the port that requests removal is removed from the IGMP snooping table. If the last port within a VLAN sends an IGMP leave message and the switch does not receive any responses to the subsequent query, then the switch immediately removes the VLAN from the multicast group. IGMP snooping is implemented primarily through ACLs, which are processed on the interfaces. These special purpose ACLs are called IGMP snooping filters. On NETGEAR 8800 series switches, the software allows you to choose between two types of IGMP snooping filters: per-port filters (the default) and per-VLAN filters. The two types of IGMP snooping filters use switch hardware resources in different ways. The two primary hardware resources to consider when selecting the IGMP snooping filters are the Layer 3 multicast forwarding table and the interface ACLs. The size of both of these hardware resources is determined by the switch model. In general, the per-port filters consume more resources from the multicast table and less resources from the ACL table. The per-VLAN filters consume less space from the multicast table and more from the ACL table. In NETGEAR 8800 series switches, the multicast table size is small, so using the per-port filters can fill up the multicast table and place an extra load on the CPU. To avoid this, configure the switch to use the per-VLAN filters. Note: The impact of the per-VLAN filters on the ACL table increases with the number of VLANs configured on the switch. If you have a large number of configured VLANs, we suggest that you use the per-port filters. Static IGMP To receive multicast traffic, a host must explicitly join a multicast group by sending an IGMP report; then, the traffic is forwarded to that host. In some situations, you might like multicast traffic to be forwarded to a port where a multicast-enabled host is not available (for example, when you test multicast configurations). Static IGMP emulates a host or router attached to a switch port, so that multicast traffic is forwarded to that port, and the switch sends a proxy join for all the statically configured IGMP groups when an IGMP query is received. You can emulate a host to forward a particular 734 | Chapter 27. Multicast Routing and Switching