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Filtering Outgoing PIM Join Messages

When the core of your network is using MPLS, PIM join and prune messages stop at the customer edge (CE) routers and are not forwarded toward the core, because these routers do not have a PIM neighbors on the core-facing interfaces. When the core of your network is using IP, PIM join and prune messages are forwarded to the upstream PIM neighbors in the core of the network.

When the core of your network is using a mix of IP and MPLS, you might want to filter certain PIM join and prune messages at the upstream egress interface of the CE routers.

You can filter PIM sparse mode (PIM-SM) join and prune messages at the egress interfaces for IPv4 and IPv6 in the upstream direction. The messages can be filtered based on the group address, source address, outgoing interface, PIM neighbor, or a combination of these values. If the filter is removed, the join will be sent after the PIM periodic join timer expires.

To filter PIM sparse mode join and prune messages at the egress interfaces, create a policy rejecting the group address, source address, outgoing interface, or PIM neighbor, and then apply the policy.

The following example filters PIM join and prune messages for group addresses 224.0.1.2 and 225.1.1.1.

  1. In configuration mode, create the policy.
    user@host# set policy-options policy-statement block-groups term t1 from route-filter 224.0.1.2/32 exactuser@host# set policy-options policy-statement block-groups term t1 from route-filter 225.1.1.1/32 exactuser@host# set policy-options policy-statement block-groups term t1 then rejectuser@host# set policy-options policy-statement block-groups term last then accept
  2. Verify the policy configuration using the show policy-options command.
    user@host# show policy-optionspolicy-statement block-groups {term t1 {from {route-filter 224.0.1.2/32 exact;route-filter 225.1.1.1/32 exact;then reject;}term last {then accept;}}
  3. Apply the PIM join and prune message filter.
    user@host> set protocols pim export block-groups
  4. After the configuration is committed, use the show pim statistics command to verify that outgoing PIM join and prune messages are being filtered.

    user@host> show pim statistics | grep filtered
    RP Filtered Source                     0
    
    Rx Joins/Prunes filtered               0
    
    Tx Joins/Prunes filtered               254
    

    The egress filter count is shown on the Tx Joins/Prunes filtered line.


Published: 2010-04-16

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