Multicast PIM - 2 RP for 2 overlapping multicast groups

[adrianfer]

On a nexus switch with PIM SM, using only static RP mapping, if i have 2 RP over 2 overlapping multicast groups, to which RP the switch will send the join message? 

1- The RP with the highest ip?

2- It will use the RP mapping line with the more specific multicast group?

3- The RP of the first RP mapping line?

Configuration example:

ip pim rp-address <RP1 ip> group-list 224.0.119.0/24
ip pim rp-address <RP2 ip> group-list 224.0.119.0/27

Which RP will use the switch if it receives a join with destination 224.0.119.1?

Thanks,

[Georg Pauwen · Accepted solution]

Hello,

the switch will use the RP mapping line with the more specific multicast group (ip pim rp-address <RP2 ip> group-list 224.0.119.0/27).

Is this an exam question ?

[adrianfer]

Nope, a real life one

My intuition also said it would use the more specific but i saw Blogs referring to other type of solution. 

[Harold Ritter]

Hi @adrianfer ,

@Georg Pauwen is right. The RP configured with the more specific multicast range would be used for overlapping multicast groups.

Regards, 

[adrianfer]

@Harold Ritter Do you mind commenting or forwarding this one to the right expert? Thanks, Adrian (ex Videotron)

[Harold Ritter · Accepted solution]

Hola Adrian,

I can definitely confirm:

NXOS# sh runn | i rp-add
ip pim rp-address 192.168.1.1 group-list 224.0.119.0/24
ip pim rp-address 192.168.1.2 group-list 224.0.119.0/27
NXOS# sh ip pim rp 224.0.119.31
PIM RP Status Information for VRF "default"
PIM RP Information for group 224.0.119.31 in VRF "default"

RP: 192.168.1.2, (0),
uptime: 00:25:53 priority: 255,
RP-source: (local),
group ranges:
224.0.119.0/27
NXOS# sh ip pim rp 224.0.119.32
PIM RP Status Information for VRF "default"
PIM RP Information for group 224.0.119.32 in VRF "default"

RP: 192.168.1.1, (0),
uptime: 00:25:58 priority: 255,
RP-source: (local),
group ranges:
224.0.119.0/24
NXOS#

Regards,

[adrianfer]

Great, thank u sir.