This section describes the multicast boundary function and implementation process.
On a network, the multicast information about each multicast group is transmitted in a specific range. This range can be considered as a Local Area Network (LAN) of the multicast information. A multicast boundary can be specified to limit the range within which multicast information is forwarded. By deploying a multicast boundary on an interface as the boundary of a BootStrap router (BSR) administrative domain, you can define a LAN for multicast information. Deploying a multicast boundary enhances multicast data security and prevents network congestion caused by multicast traffic forwarding within a large range.
After a multicast boundary is configured for a specific multicast group on an interface, the interface cannot receive or send multicast packets for the multicast group. To better support source-specific multicast (SSM), you can configure multicast boundary policies in which a source- and group-specific boundary is specified. In addition, a multicast boundary policy can be used to filter uni-directional traffic.
If a multicast packet matches the filtering criteria on an interface where a multicast boundary is configured, the multicast packet is filtered. A multicast boundary can be defined in either of the following modes:
Based on a multicast group address range: A multicast boundary is configured based on group addresses and mask lengths that are configured on an interface. An interface that is configured with a multicast boundary filters multicast data packets, BSR messages, PIM Join/Prune messages, and IGMP Report messages.
Based on a multicast boundary policy: A multicast boundary is configured based on an ACL on an interface. Three types of multicast boundary policies can be configured based on the directions of packets to be filtered.
Inbound multicast boundary policy: filters the multicast data packets that an interface can receive and the PIM Join/Prune and IGMP Report messages that an interface can send. By filtering these messages, an inbound multicast boundary policy controls the direction in which multicast data is forwarded and received on the protocol control and forwarding planes.
Outbound multicast boundary policy: filters the PIM Join/Prune and IGMP Report messages that an interface can receive. By filtering these messages, an outbound multicast boundary policy controls the downstream interfaces in the downstream interface list of multicast forwarding entries.
Inbound and outbound multicast boundary policy: filters the packets, including auto-rendezvous point (auto-RP) packets that an interface can receive and send. Auto-RP packets are filtered based on group information.