bsr vs static rp selection

Farooq Muhammad · ‎04-16-2013

Hello to All,

I have a network in which previously a router named R1 was the rp for all multicast groups and propagated to other routers through BSR now i reconfigured this and nominated it to be the RP through BSR but excluded some multicast groups.For the excluded groups i made another router R2 to be the rp configured statically and all network elements were statically informed about the new rp for the said groups.The network devices shows they have two rps as per configuration i-e one through bsr and another static but when checked through mroute and other commands the old rp is still acting as rp for all groups.Any suggestions?please.

Regards

Farooq

Andre Gustavo Albuquerque · ‎04-16-2013

Farooq,

Diagrams and command outputs would help to have a better visibility on what's happening.

If the c-RP information was really propagated from BSR to all routers and this information is not reflected on mrib, it may be a case for using a "clear ip mroute" command to force the information to be reprocessed.

Make sure you read the document about BSR on CLN, located here.

Best regards, Gustavo

Giuseppe Larosa · ‎04-20-2013

Hello Farooq,

I hope you are well.

What you see is normal and expected : each PIM router prefers a dynamic source of information about RP mapping like Bootstrap protocol over manually configured RP.

Having already deployed a BSR router the best option is to use bootstrap protocol for both candidate RPs R1 and R2.

In each of R1,R2 you can use the command

ip pim [ vrf vrf-name ] rp-candidate interface-type interface-number [bidir] [ group-list access-list ] [ interval seconds ] [ priority value ]

More specifically you need (let's suppose you are using a loopback for the RP address recommended)

ip pim rp-candidate loopback0 group-list 4

where 4 is a standard ACL thst describes the range(s) of group addresses for which the local node will be an RP candidate.

like

access-list 4 permit 239.0.0.0 0.255.255.255

see

http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti/command/imc_i3.html#wp3772039226

All you need to do is to use a different ACL on R1 and R2.

The BSR will receive the advertisements and will propagate them to all the routers without the need to use manual RP.

An alternative method is to add the option override to the manual RP command, but this would need to be done on all routers. The method described above requires changes only on R1 and R2.

for the override option see

http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti/command/imc_i3.html#wp1566088322

override

(Optional) Specifies that if dynamic and static group-to-RP mappings are used together and there is an RP address conflict, the RP address configured for a static group-to-RP mapping will take precedence.

Note

If the override keyword is not specified and there is RP address conflict, dynamic group-to-RP mappings will take precedence over static group-to-RP mappings.

I recommend to use the first method because you have already deployed the bootstrap protocol and you have a BSR router ( It is recommended to have a secondary BSR router ready to take over if the primary fails, this is supported by bootstrap protocol)

Hope to help

Giuseppe