Configuring Register Message Filters on a PIM RP and DR

PIM register messages are sent to the rendezvous point (RP) by a designated router (DR). When a source for a group starts transmitting, the DR sends unicast PIM register packets to the RP.

Register messages have the following purposes:

• Notify the RP that a source is sending to a group.
• Deliver the initial multicast packets sent by the source to the RP for delivery down the shared path tree (SPT).

The PIM RP keeps track of all active sources in a single PIM sparse mode domain. In some cases, more control over which sources an RP knows about, or which sources a DR tells other RPs about, is desired. A high degree of control over PIM register messages is provided by RP/DR register message filtering. Message filtering prevents unauthorized groups and sources from registering with an RP router.

You configure RP/DR register message filtering to control the number and location of multicast sources that an RP knows. You can apply register message filters on a DR to control outgoing register messages, or apply them on an RP to control incoming register messages.

When anycast RP is configured, all RPs in the anycast RP set need to be configured with the same register message filtering policy.

You can configure message filtering globally or for a routing instance. These examples shows the global configuration.

To configure an RP filter to drop the register packets for multicast group range 224.1.1.0/24 from source address 10.10.94.2:

1. On the RP, configure the policy.
   user@host# edit policy-options policy-statement incoming-policy-for-rp fromuser@host# set route-filter 224.1.1.0/24 orlongeruser@host# set source-address-filter 10.10.94.2/32 exactuser@host# set then rejectuser@host# exit
2. Apply the policy to the RP.
   user@host# edit protocols pim rpuser@host# set rp-register-policy incoming-policy-for-rpuser@host# set local address 10.10.10.5user@host# exit

To configure a DR filter to prevent sending register packets for group range 224.1.1.0/24 and source address 10.10.10.1/32:

1. On the DR, configure the policy.
   user@host# edit policy-options policy-statement outgoing-policy-for-rpuser@host# set from route-filter 224.1.1.0/24 orlongeruser@host# set from source-address-filter 10.10.10.1/32 exactuser@host# set then rejectuser@host# exit
2. Apply the policy to the DR.

   The static address is the address of the RP to which you do not want the DR to send the filtered register messages.

   user@host# edit protocols pim rpuser@host# set dr-register-policy outgoing-policy-for-druser@host# set static 10.10.10.3user@host# exit

To configure a policy expression to accept register messages for multicast group 224.1.1.5 but reject those for 224.1.1.1:

1. On the RP, configure the policies.
   user@host# edit policy-options policy-statement reject_224_1_1_1user@host# set from route-filter 224.1.1.0/24 orlongeruser@host# set from source-address-filter 10.10.94.2/32 exactuser@host# set then rejectuser@host# exit
   user@host# edit policy-options policy-statement accept_224_1_1_5user@host# set term one from route-filter 224.1.1.5/32 exactuser@host# set term one from source-address-filter 10.10.94.2/32 exactuser@host# set term one then acceptuser@host# set term two then rejectuser@host# exit
2. Apply the policies to the RP.
   user@host# edit protocols pim rpuser@host# set rp-register-policy [ reject_224_1_1_1 | accept_224_1_1_5 ]user@host# set local address 10.10.10.5

To monitor the operation of the filters:

1. Run the show pim statistics command. The command output contains the following fields related to filtering:
   • RP Filtered Source
   • Rx Joins/Prunes filtered
   • Tx Joins/Prunes filtered
   • Rx Register msgs filtering drop
   • Tx Register msgs filtering drop

Related Topics

• PIM Sparse-Mode Source Registration
• Filtering RP/DR Register Messages
• show pim statistics in the Routing Protocols and Policies Command Reference