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Filtering Unwanted IGMP Reports at the IGMP Interface Level

Suppose you need to limit the subnets that can join a certain multicast group. The group-policy statement enables you to filter unwanted IGMP reports at the interface level. When this statement is enabled on a router running IGMP version 2 (IGMPv2) or version 3 (IGMPv3), after the router receives an IGMP report, the router compares the group against the specified group policy and performs the action configured in that policy (for example, rejects the report if the policy matches the defined address or network).

You define the policy to match only IGMP group addresses (for IGMPv2) by using the policy's route-filter statement to match the group address. You define the policy to match IGMP (source, group) addresses (for IGMPv3) by using the policy's route-filter statement to match the group address and the policy's source-address-filter statement to match the source address.

To filter unwanted IGMP reports:

  1. Configure an IGMPv2 policy.
    [edit policy-statement reject_policy_v2]user@host# set from route-filter 224.1.1.1/32 exactuser@host# set from route-filter 239.0.0.0/8 orlongeruser@host# set then reject
  2. Configure an IGMPv3 policy.
    [edit policy-statement reject_policy_v3]user@host# set from route-filter 224.1.1.1/32 exactuser@host# set from route-filter 239.0.0.0/8 orlongeruser@host# set from source-address-filter 10.0.0.0/8 orlongeruser@host# set from source-address-filter 127.0.0.0/8 orlongeruser@host# set then reject
  3. Apply the policies to the IGMP interfaces on which you prefer not to receive specific group or (source, group) reports. In this example, ge-0/0/0.1 is running IGMPv2, and ge-0/1/1.0 is running IGMPv3.
    [edit protocols igmp]user@host# set interface ge-0/0/0.1 group-policy reject_policy_v2user@host# set interface ge-0/1/1.0 group-policy reject_policy_v3
  4. Verify the operation of the filter by checking the Rejected Report field in the output of the show igmp statistics command.
 

Related Documentation

 

Published: 2014-07-23

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