Multicast Routing - Selecting RPS

In this post i look at auto rp and how the mapping agent can be used to select specific RPs for specified groups.

This requires the use of the command ip pim rp-announce-filter on the mapping agent. The rp-announce filter needs to match the send-rp-announce
filter used by the RPs. If the groups requested by the RP do not match the mapping agent’s filters, non matching groups are discarded.

Example:


R1 (MAPPING AGENT)
interface Loopback0
ip pim sparse-dense-mode
!
ip pim send-rp-discovery Loopback0 scope 16
ip pim rp-announce-filter rp-list 1 group-list 2
!
access-list 1 permit 150.1.3.3
access-list 2 permit 239.0.0.0 0.255.255.255


R3 (CANDIDATE RP)
interface Loopback0
ip pim sparse-dense-mode
!
ip pim send-rp-announce Loopback0 scope 16 group-list 50
!
access-list 50 permit 239.0.0.0 0.255.255.255


post script.
If the rp-announce-filter does not match an rp then NO filtering is applied. That is for filtering to take place a positive match is first required on the RP within the RP list. Hence to filter RP multicast groups announced by an RP it is first necessary to match the RP and specify the allowed multicast groups. If the RP is denied in the RP list then NO filtering is applied!!