Cisco IGMP Proxy Configuration Guide: Setting Up Multicast Routing (EN)

IGMP Proxy

Configuring IGMP Proxy Prerequisites for IGMP Proxy, on page 1 Information About IGMP Proxy, on page 1 How to Configure IGMP Proxy, on page 4 Configuration Examples for IGMP Proxy, on page 9 Additional References for IGMP Proxy, on page 10 Feature History for IGMP Proxy, on page 11 Prerequisites for IGMP Proxy • All devices on the IGMP UDL have the same subnet address. If all devices on the UDL cannot have the same subnet address, the upstream device must be configured with secondary addresses to match all of the subnets to which the downstream devices are attached. • IP multicast is enabled and the PIM interfaces are configured.

When you are configuring PIM interfaces for IGMP proxy, use PIM sparse mode (PIM-SM) when the interface is operating in a sparse-mode region and you are running static RP, bootstrap (BSR), or Auto-RP with the Auto-RP listener capability. Information About IGMP Proxy The following sections provide information about IGMP proxy. IGMP Proxy An IGMP proxy enables hosts in a unidirectional link routing (UDLR) environment that are not directly connected to a downstream router to join a multicast group sourced from an upstream network. There are two methods of implementing IGMP Proxy: • IGMP Proxy for a Single Upstream Interface • IGMP Proxy for Multiple Upstream Interfaces Configuring IGMP Proxy 1

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IGMP Proxy for a Single Upstream Interface

IGMP Proxy for a Single Upstream Interface The figure below illustrates a sample topology that shows two UDLR scenarios: • Traditional UDL routing scenario--A UDL device with directly connected receivers. • IGMP proxy scenario--UDL device without directly connected receivers. IGMP UDLs are needed on the upstream and downstream devices. Although the following illustration and example uses routers in the configuration, any device (router or switch) can be used. Note Scenario 1 - Traditional UDLR Scenario (UDL Device with Directly Connected Receivers) For scenario 1, no IGMP proxy mechanism is needed. In this scenario, the following sequence of events occurs: 1.

User 2 sends an IGMP membership report requesting interest in group G. 2. Router B receives the IGMP membership report, adds a forwarding entry for group G on LAN B, and proxies the IGMP report to Router A, which is the UDLR upstream device. 3. The IGMP report is then proxied across the Internet link. 4. Router A receives the IGMP proxy and maintains a forwarding entry on the unidirectional link. Configuring IGMP Proxy IGMP Proxy for a Single Upstream Interface Configuring IGMP Proxy 2

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IGMP Proxy for Multiple Upstream Interfaces

Scenario 2 - IGMP Proxy Scenario (UDL Device without Directly Connected Receivers) For scenario 2, the IGMP proxy mechanism is needed to enable hosts that are not directly connected to a downstream device to join a multicast group sourced from an upstream network. In this scenario, the following sequence of events occurs: 1. User 1 sends an IGMP membership report requesting interest in group G. 2. Router C sends a PIM Join message hop-by-hop to the RP (Router B). 3. Router B receives the PIM Join message and adds a forwarding entry for group G on LAN B. 4. Router B periodically checks its mroute table and proxies the IGMP membership report to its upstream UDL device across the Internet link.

5. Router A creates and maintains a forwarding entry on the unidirectional link (UDL). In an enterprise network, it is desirable to be able to receive IP multicast traffic via satellite and forward the traffic throughout the network. With unidirectional link routing (UDLR) alone, scenario 2 would not be possible because receiving hosts must be directly connected to the downstream device, Router B. The IGMP proxy mechanism overcomes this limitation by creating an IGMP report for (*, G) entries in the multicast forwarding table.

To make this scenario functional, therefore, you must enable IGMP report forwarding of proxied (*, G) multicast static route (mroute) entries (using the ip igmp mroute-proxy command) and enable the mroute proxy service (using the ip igmp proxy-service command) on interfaces leading to PIM-enabled networks with potential members. Because PIM messages are not forwarded upstream, each downstream network and the upstream network have a separate domain. Note IGMP Proxy for Multiple Upstream Interfaces IGMP proxy also enables the user to request data from multiple upstream interfaces. You can implement IGMP proxy by this method if there are more number of upstream devices in the network.

With this method, you can also implement IGMP proxy for a single upstream device as in any of the three scenarios described in the previous section. Configuring IGMP Proxy IGMP Proxy for Multiple Upstream Interfaces Configuring IGMP Proxy 3

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Configuring the Upstream UDL Device for IGMP UDLR

In this method, IGMP proxy is used to enable the user to receive traffic from multiple upstream devices. The following sequence of events occurs: 1. The host is in PIM Domain 1 and sends multiple IGMP membership reports (join requests) to Router C requesting interest in different groups. Router C converts the IGMP joins to PIM joins and sends them to Router B . These requests should be sent upstream, from Router B to Router A . The routers are in two different PIM domains (not PIM neighbors). 2. Router B converts the PIM join messages to IGMP proxy joins so that it can be forwarded to the upward interfaces. 3. A class-map is configured globally.

This class-map describes the information about multicast groups. The IGMP proxy joins for different multicast groups are sent if the following conditions are met: • There is (*, G) or and (S, G) entry for that group. • (*, G) or the (S, G) entry has a NON-NULL OIF list. 4. During the IGMP proxy intervals, the IGMP proxy joins for different groups are sent through the respective upstream interfaces. 5. After the IGMP proxy join reaches Router A , it is forwarded to the different source devices as PIM join messages. How to Configure IGMP Proxy Configuring the Upstream UDL Device for IGMP UDLR Perform this task to configure the upstream UDL device for IGMP UDLR.

Configuring IGMP Proxy How to Configure IGMP Proxy Configuring IGMP Proxy 4

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