MSDP on NXOS and in general - PIM on loopback (source)

[Bilal Nawaz]

I was just talking to my colleagues and we were thinking about the need for enabling PIM on the loopback used as source for MSDP connections (yes indeed we do need it for MSDP to work) but why? Do the loopbacks become a "transit path" for multicast traffic?

Thank you

Bilal

[Jon Marshall]

Hi Bilal

I haven't used MSDP before so is your question specifically about that or a more general one about enabling PIM on the loopback interface you use as the RP address ?

Jon

[Bilal Nawaz]

Hi Jon, yes the question is specifically around MSDP, the source loopback is a separate one, from the one used for RP.

Bilal

EDIT: Im just having a read of this - http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus9000/sw/6-x/multicast/configuration/guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide/b_Cisco_Nexus_9000_Series_NX-OS_Multicast_Routing_Configuration_Guide_chapter_0101.pdf

I think I need to read it couple of times to understand, but answer might be there.

[Jon Marshall]

Hi Bilal

I didn't respond before because I wanted to see if others contributed.

The configurations I have seen using MDSP do not require PIM to be enabled on the interface used as the source IP address for the MDSP peering.

This is because it is simply an IP used for peering and nothing else as far as I know.

May not be of any use to you but just thought I add that.

Jon

[Bilal Nawaz]

Hi Jon, thanks for replying, and this is exactly our point!!!

On the C6Ks we hadn't configured pim on those loopbacks used for peering, however seems as though to get MSDP to work correctly on NXOS we must enable pim.

Unless something funky is goin'on. Will have another look on Monday.

[Jon Marshall]

however seems as though to get MSDP to work correctly on NXOS we must enable pim.

Wouldn't surprise me, seems like a lot things are "slightly" different on the Nexus switches :-)

Jon