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# MLD Proxy Overview

MLD proxy enables the router to issue MLD host messages on behalf of hosts that the router discovered through standard MLD interfaces. The router acts as a proxy for its hosts. The E Series router supports MLD proxy versions 1 and 2.

Figure 20 shows a router in an MLD proxy configuration. You enable MLD proxy on one interface, which connects to a router closer to the root of the tree. This interface is the upstream interface. The attached upstream router on the upstream interface should be running MLD.

You enable MLD 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 20: Upstream and Downstream Interfaces

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

- When queried, sends multicast listener reports to the group.
- When one of its hosts joins a multicast address group to which none of its other hosts belong, sends unsolicited multicast listener reports to that group.
- When the last of its hosts in a particular multicast group leaves, the group sends either an unsolicited multicast listener done report to the all-routers address (FF02::2) for MLDv1 or an MLDv2 multicast listener report to the all-MLDv2 routers address (FF02::16).

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