RackSwitch G8000 Application Guide
IGMP Snooping
IGMP Snooping allows the switch to forward multicast traffic only to those ports that request it. IGMP Snooping prevents multicast traffic from being flooded to all ports. The switch learns which server hosts are interested in receiving multicast traffic, and forwards it only to ports connected to those servers.
IGMP Snooping conserves bandwidth. With IGMP Snooping, the switch learns which ports are interested in receiving multicast data, and forwards multicast data only to those ports. In this way, other ports are not burdened with unwanted multicast traffic.
The switch can sense IGMP Membership Reports from attached clients and act as a proxy to set up a dedicated path between the requesting host and a local IP Multicast router. After the pathway is established, the switch blocks the IP Multicast stream from flowing through any port that does not connect to a host member, thus conserving bandwidth.
The
An IP Multicast Router (Mrouter) sends Membership Queries to the switch, which for- wards them to all ports in a given VLAN.
Hosts that want to receive the multicast data stream send Membership Reports to the switch, which sends a proxy Membership Report to the Mrouter.
The switch sets up a path between the Mrouter and the host, and blocks all other ports from receiving the multicast.
Periodically, the Mrouter sends Membership Queries to ensure that the host wants to con- tinue receiving the multicast. If a host fails to respond with a Membership Report, the Mrouter stops sending the multicast to that path.
The host can send a Leave Report to the switch, which sends a proxy Leave Report to the Mrouter. The multicast path is terminated immediately.
The G8000 supports the following IGMP capacities:
IGMP version 1, 2, and 3
1024 VLANs
128 Mrouters
512 multicast groups
NOTE – Unknown multicast traffic is sent to an Mrouter port only if the flood option is disabled. To enable or disable IGMP flood, use the following command:
RS G8000 (config)# [no] ip igmp flood
130 Chapter 9: IGMP | BMD00041, November 2008 |
