bsr backup rp

From: CCIE unnumbered (ccie.unnumbered@gmail.com)
Date: Fri Sep 12 2008 - 13:18:15 ART


R2 and R3 are 3560 switches running layer 3 ip routing.
R5 is a 2811 router. In the beginning, R3 is the BSR RP because its
participating IP address is the highest.

R3:
ip multicast-routing distributed
interface Loopback0
 ip address 172.16.56.3 255.255.255.255
 ip pim sparse-mode
 ip igmp join-group 224.1.1.1
 ip igmp join-group 224.2.2.2
ip pim bsr-candidate Loopback0 0 192
ip pim rp-candidate Loopback0

R2:
ip multicast-routing distributed
interface Loopback0
 ip address 172.16.56.2 255.255.255.255
 ip pim sparse-mode
 ip igmp join-group 224.1.1.1
ip pim bsr-candidate Loopback0 0 192
ip pim rp-candidate Loopback0

After R3#no ip multicast-routing distributed
The following are expected:
R2#sh ip pim rp
Group: 224.2.2.2, RP: 172.16.56.2, v2, next RP-reachable in 00:01:00
Group: 224.1.1.1, RP: 172.16.56.2, v2, next RP-reachable in 00:01:00
R5#sh ip pim rp
Group: 224.2.2.2, RP: 172.16.56.2, v2, uptime 00:02:28, expires 00:01:35
Group: 224.1.1.1, RP: 172.16.56.2, v2, uptime 00:02:28, expires 00:01:35

So far, so good.

Now, after the following command:
R2#no ip pim rp-cand lo0

I do not understand the following outputs:
R2#sh ip pim rp
Group: 224.2.2.2, RP: 172.16.56.3, v2, uptime 00:03:11, expires 00:02:23
Group: 224.1.1.1, RP: 172.16.56.3, v2, uptime 00:03:11, expires 00:02:23

R5#sh ip pim rp
Group: 224.2.2.2, RP: 172.16.56.3, v2, uptime 00:05:48, expires 00:02:07
Group: 224.1.1.1, RP: 172.16.56.3, v2, uptime 00:05:48, expires 00:02:07

Why R3 resumes the RP role while its multicast routing is turned off?

thanks,
CCIE unnumbered

Blogs and organic groups at http://www.ccie.net



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