Filtering Incoming PIM Join Messages
While multicast scopes prevent the actual multicast data packets from flowing in or out of an interface, PIM join filters prevent a state from being created in a router. A state—the (*,G) or (S,G) entries—is the information used for forwarding unicast or multicast packets. Using PIM join filters prevents the transport of multicast traffic across a network and the dropping of packets at a scope at the edge of the network. Also, PIM join filters reduce the potential for denial-of-service (DoS) attacks and PIM state explosion—large numbers of PIM join messages forwarded to each router on the rendezvous-point tree (RPT), resulting in memory consumption.
To use PIM join filters to efficiently restrict multicast traffic from certain source addresses, create and apply the routing policy across all routers in the network. See Table 1 for a list of match conditions.
Table 1: PIM Join Filter Match Conditions
Match Condition | Matches On |
|---|---|
interface | Router interface or interfaces specified by name or IP address |
neighbor | Neighbor address (the source address in the IP header of the join and prune message) |
route-filter | Multicast group address embedded in the join and prune message |
source-address-filter | Multicast source address embedded in the join and prune message |
To create a routing policy to reject a PIM join request for a source, include a policy name at the [edit policy-options policy-statement] or [edit logical-systems logical-system-name policy-options policy-statement] hierarchy level.
To apply one or more policies to routes being imported into the routing table from PIM, include the import statement:
For a list of the hierarchy levels at which you can include this statement, see the statement summary section for this statement.
For a PIM join filter example, see Example: Filtering Incoming PIM Join Messages.
 | Note: Configuring multicast scoping on all routers filters the actual data and might be preferable to a PIM join filter solution. For more information about multicast scoping, see Multicast Scoping Overview. |
