Multicast PIM Accept RP

Lessons Discussion
1

This topic is to discuss the following lesson:

2

Hi Rene,

What is the different PIM accept RP and below configuration? The PIM accept RP applicable for static RP, Auto Rp and BSR?

Ip PIM send-rp-annouce loopback 0 scope 10 group-list 1

Davis

3

Hi Davis,

PIM accept RP can be used to tell your router not to accept just any RP. I believe it works for AutoRP and BSR, not for static RPs. For example when there are 10 routers in your network advertising themselves as the RP then you can use this command to ignore a couple of them.

ip pim send-rp-announce is used to configure your router to advertise itself as an RP, the access-list is used to advertise the networks that you want to be a RP for.

Rene

4

Got it.

Thanks Rene.

Davis

5

Hi Rene,

Is 192.168.12.1 the address of the loopback of R1?

Groeten,

Hans.

6

Hi Hans,

192.168.12.1 is the IP address of R1. I usually use subnets / IP addresses like this:

192.168.XY.X where X = R1 and Y = R2.

For loopbacks I use 1.1.1.1/32 for R1, 2.2.2.2/32 for R2 etc.

Rene

7

Hi Rene,

What if I sourced the Multicast traffic from R1 Loopback, will it accept, for my lab its not accept and showing RPF failed or RP failed from debug, even though R2 has correc RPF.

Regards
Jam

8

Hi Jam,

It doesn’t matter if you use a loopback or “regular” interface as the source as long the RPF check is correct. It’s difficult to tell what is wrong without seeing your config.

1 Like
9

I believe the picture should be updated using 192.168.12.1 for R1 and .2 for R2.

Thank you,
Stefanita

10

Hi Stefanita,

That’s right, thanks for letting us know. Just fixed this.

Rene

1 Like
11

Hi Rene,

Your lab found at https://gns3vault.com/multicast/multicast-pim-accept-rp is a better example of this exercise. The difference here that you used a standard ACL with the word “GROUPS” as opposed to numbers. Either way, thank you for both examples.

Jay K.

1 Like
12

We will also need to allow 224.0.1.40 address, as this is used for RP.
If not allowed below log is noticed.

R1#
*Mar  1 01:41:51.139: %PIM-6-INVALID_RP_JOIN: Received (*, 224.0.1.40) Join from 192.168.12.2 for invalid RP 1.1.1.1
13

Hello Syed

I tried labbing this up again, and after some time, I did get the same error message you mention. Even so the RP does appear correct in both routers. I will let Rene know to see if the lesson needs adding to…

Thanks for pointing that out!

Laz

14

Hi Syed,

224.0.1.40 is for messages from the AutoRP mapping agent. We don’t need it here because we use a static RP.

I think you can disable AutoRP now on Cisco IOS 15.x with the no ip pim auto-rp command.

Rene

15

Thanks for the reply

16

Hi,

I think also configs on R1 and R2 have to be modified as on eth0 shows 192.168.12.2 and 3

Thanks

17

Hello Stefano

Yes, you are correct, I will let Rene know to make the changes…

Thanks again!

Laz

18

Hi,

I was reading some of the older replies and it seems there is an answer to a question I had:

But I just want to clarify that I understand it what is being said, which is that even though the lesson has applied the accept-rp command to the RP, it should actually be applied to the LHR - where there’s a receiver - to stop it from sending Joins to the RP in the first place. Is that correct?

Thanks.

Sam

19

Hello Sam

The accept-rp feature should be applied to any router that will potentially be an LHR. That can also include the RP, which is where it was applied in the lesson. In the lesson, this was used as an example to observe the behavior.

Best practice dictates that you should apply it to any LHR where you want to control which RP is chosen.

I hope this has been helpful!

Laz

1 Like