IP multicast AnyCast RP

Answered Question
Mar 27th, 2006

When configuring Loopback 1 as the RP address, do I also put 'ip pim sparse-mode' on the loopback interface?

Here is what I have on two routers I want to be the RP's using AnyCast RP and MSDP:

1. Router-1 (6509 IOS 12.2(18)

interface Loopback0

ip address 164.72.239.5 255.255.255.255

ip pim sparse-mode

interface Loopback1

ip address 164.72.239.42 255.255.255.255

ip pim sparse-mode

ip msdp peer 164.72.239.18 connect-source Loopback0

ip msdp cache-sa-state

ip msdp originator-id Loopback0

ip pim rp-address 164.72.239.42

ip pim accept-rp 164.72.239.42

2. Router-2 (7206-XVR IOS (12.2)

interface Loopback0

ip address 164.72.239.18 255.255.255.255

ip pim sparse-mode

interface Loopback1

ip address 164.72.239.42 255.255.255.255

ip pim sparse-mode

ip msdp peer 164.72.239.5 connect-source Loopback0

ip msdp originator-id Loopback0

ip pim rp-address 164.72.239.42 1

ip pim accept-rp 164.72.239.42 1

I have this problem too.
0 votes
Correct Answer by bhedlund about 8 years 11 months ago

OK Jim, I just blew the dust off my Routing TCP/IP Volume II book and opened to the chapter on Multicast routing. After flipping through a few pages I would like to retract my earlier statement about the PIM configuration on Loopback interfaces for Anycast-RP. Sine the loopback interface used for Anycast-RP is necessary to PIM functionality, Yes, you should configure 'ip pim sparse-dense-mode' on this interface.

Loopback interfaces used for MSDP peering however do not need PIM configuration as these intefaces are not essential to PIM functionality.

As for your second question, 'ip pim accept-rp' is only needed if you wish to filter the (*,G) joins handled by the RP. It is not required for basic functionality.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tip3r/ip3_i2gt.htm#wp1068530

Hope this helps.

Please rate all helpful posts.

Regards,

Brad

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jkeeffe Mon, 03/27/2006 - 11:02

Thanks Brad - I didn't think you'd need to do that but what about the example in this document..

http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/mcst_sol/rps.htm#wp1029526

...where it shows this:

Router 72a

ip multicast-routing

interface Loopback0

ip address 20.0.0.3 255.255.255.255

ip pim sparse-mode

interface Loopback1

ip address 20.0.0.1 255.255.255.255

ip pim sparse-mode

ip pim rp-address 20.0.0.1

ip msdp peer 20.0.0.2 connect-source Loopback0

ip msdp mesh-group anycast 20.0.0.2

ip msdp originator-id Loopback0

bhedlund Mon, 03/27/2006 - 12:18

I have seen a lot of sample configs like this that show you more than what it is needed.

Believe me, I was wrong, about 10 other NetPro posters here would have jumped all over me by now. :)

Please rate all helpful posts.

Regards,

Brad

jkeeffe Mon, 03/27/2006 - 13:49

Thanks again Brad.

If I could ask one more question.

Other then the 'ip pim rp-address xxx.xxx.xxx.xxx', do I need the statement 'ip pim accept-rp xxx.xxx.xxx.xxx' on the non-rp routers in a basic anycast encironment? I'm not trying to segregate which RP's handle what mcast groups.

Correct Answer
bhedlund Mon, 03/27/2006 - 15:55

OK Jim, I just blew the dust off my Routing TCP/IP Volume II book and opened to the chapter on Multicast routing. After flipping through a few pages I would like to retract my earlier statement about the PIM configuration on Loopback interfaces for Anycast-RP. Sine the loopback interface used for Anycast-RP is necessary to PIM functionality, Yes, you should configure 'ip pim sparse-dense-mode' on this interface.

Loopback interfaces used for MSDP peering however do not need PIM configuration as these intefaces are not essential to PIM functionality.

As for your second question, 'ip pim accept-rp' is only needed if you wish to filter the (*,G) joins handled by the RP. It is not required for basic functionality.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios123/123tcr/123tip3r/ip3_i2gt.htm#wp1068530

Hope this helps.

Please rate all helpful posts.

Regards,

Brad

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