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# IGMP Proxy Overview

IGMP proxy enables the router to issue IGMP host messages on behalf of hosts that the router discovered through standard IGMP interfaces. The router acts as a proxy for its hosts. E-series routers support IGMP proxy versions 2 and 3.

Figure 7 shows a router in an IGMP proxy configuration. You enable IGMP proxy on one interface, which connects to a router closer to the root of the tree. This interface is the upstream interface. The router on the upstream interface is running IGMP.

You enable IGMP on the interfaces that connect the router to its hosts that are farther away from the root of the tree. These interfaces are known as downstream interfaces.

Figure 7: Upstream and Downstream Interfaces

As described in IGMP Overview, earlier in this chapter, hosts interact with the router through the exchange of IGMP messages. Similarly, when you configure IGMP proxy, the router interacts with the router on its upstream interface through the exchange of IGMP messages. However, when acting as the proxy, the router performs the host portion of the IGMP task on the upstream interface, as follows:

- When queried, sends group membership reports to the group.
- When one of its hosts joins a multicast address group to which none of its other hosts belong, sends unsolicited group membership reports to that group.
- When the last of its hosts in a particular multicast group leaves the group, sends an unsolicited leave group membership report to the all-routers group (244.0.0.2).

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