Configuring IGMP
Before you begin:
- Determine whether the router is directly attached to any multicast sources. Receivers must be able to locate these sources.
- Determine whether the router is directly attached to any multicast group receivers. If receivers are present, IGMP is needed.
- Determine whether to configure multicast to use sparse, dense, or sparse-dense mode. Each mode has different configuration considerations.
- Determine the address of the RP if sparse or sparse-dense mode is used.
- Determine whether to locate the RP with the static configuration, BSR, or auto-RP method.
- Determine whether to configure multicast to use its own RPF routing table when configuring PIM in sparse, dense, or sparse-dense mode.
- Configure the SAP and SDP protocols to listen for multicast session announcements. See Configuring the Session Announcement Protocol.
To configure the Internet Group Management Protocol (IGMP), include the igmp statement:
You can include this statement at the following hierarchy levels:
- [edit protocols]
- [edit logical-systems logical-system-name protocols]
By default, IGMP is enabled on all interfaces on which you configure Protocol Independent Multicast (PIM), and on all broadcast interfaces on which you configure the Distance Vector Multicast Routing Protocol (DVMRP).
 | Note: You can configure IGMP on an interface without configuring PIM. PIM is generally not needed on IGMP downstream interfaces. Therefore, only one “pseudo PIM interface” is created to represent all IGMP downstream (IGMP-only) interfaces on the router. This reduces the amount of router resources, such as memory, that are consumed. You must configure PIM on upstream IGMP interfaces to enable multicast routing, perform reverse-path forwarding for multicast data packets, populate the multicast forwarding table for upstream interfaces, and in the case of bidirectional PIM and PIM sparse mode, to distribute IGMP group memberships into the multicast routing domain. |
