PIM - BSR

PIM BSR (Bootstrap Routing) - the basics

The BSR mechanism is a nonproprietary method of defining RPs that can be used with third-party routers. There is no configuration necessary on every router separately (except on candidate-BSRs and candidate-RPs). The canidate-RPs are analagous with Auto-RP candidate RPs and the candidate-BSRs are analagous with the Auto RP mapping agent.

Thes can be defined as follows.

R1
ip pim rp-candidate Loopback0

R3
ip pim rp-candidate Loopback0

R5
ip pim bsr-candidate Loopback0 31


Router_5#show ip pim rp-hash 224.1.1.1
RP 150.1.7.7 (?), v2
Info source: 155.1.37.7 (?), via bootstrap, priority 0, holdtime 150
Uptime: 00:15:07, expires: 00:02:21
PIMv2 Hash Value (mask 255.255.255.254)
RP 150.1.7.7, via bootstrap, priority 0, hash value 1852227743
RP 150.1.9.9, via bootstrap, priority 0, hash value 800581801

Multicast - BSR

I recently came across a lab scenario where 3 routers were operating in PIM Sparse mode. The question stated that an interface on one router should join a multicast group and all other routers should be able to ping this address.

The sting in the tail was that the configuration must be achieved on only 1 router and the 'ip pim autorp listener' command could NOT be used.

The obvious answer would have been to have configured auto rp. However a pre-requisite for this to work in a PIM sparse mode environment would be for the 'ip pim autorp listener' command to be configured on all routers in the domain.

The way around this problem is to configure BSR (bootstrap routing). This can operate in sparse mode without the 'autorp listener' prerequisite.

Therefore on one of the routers the place the following configuration

ip pim rp-candidate lo0
ip pim bsr-candidate lo0