Multicast routing paths and RPs

[AK59]

Dear all, 

I'm actually having some trouble trying to figure out how could I handle the move of a line with a customer using Multicast routing. I tried to synthetize a bit with the below diagram. 

Here is my problem : 

I actually have traffic from Multicast Router reaching the RP in customer network passing through Router 1. 

The line between Router 1 and the customer network will soon be shut and moved between customer network and Router 2. 

There is nothing wrong about that, but I really need to validate the multicast traffic (and reach the RP) between Router 2 and nustomer network before shutting the old line...

The problem is multicast routing allows us to use only route to the RP(Shortest Path tree)...so if i'm adding routes to RP from Router 2 (which has better metric than Router 1), then the traffic will go through Router 2 and it will impact application because the environment around Router 2 is not ready...any ideas everyone ? 

 

[Giuseppe Larosa]

Hello @AK59 ,

you could try to use an ip mroute towards the RP address on the multicast router downstream pointing to the  Router 2.

This should not change your unicast routing.

Hope to help

Giuseppe

[Joseph W. Doherty]

Giuseppe's is likely the best suggestion, but another (possible?) suggestion would be to move the RP (to router 2?). Multicast will first go to the RP before moving to SPF between source and destination (and the latter multicast flow migration, I recall [?], can be disabled or possibly delayed).

[AK59]

Thanks for your contribution, could you be more precise with the ip mroute? 

For example, in the Router 1 I have the following configuration

ip pim rp-address 10.10.10.10
[...]
ip route 10.10.10.0 255.255.255.0 Tunnel1

(Tunnel1 is the final exit reaching the customer network) 

Router 1 and Router 2 are on the same vrf so sharing the same routing table.

Router 2 will reach the customer network with a tunnel too ( let's call it Tunnel2), what would the configuration would look like on Router 2 ? 

I'm a bit confused about how the mroute differs from the pim sparse mode...

Thanks in advance, 

[Giuseppe Larosa]

Hello @AK59 ,

the

ip mroute 10.10.10.10 255.255.255.255  <R2-hext-hop>

has to be configured on the router that is downstream more internal of both R1 and R2.

The ip mroute create a multiast static route that is used to perform the reverse path check towards the source/RP address.

This is the idea for this suggestion.

Hope to help

Giuseppe

[AK59]

Hi Giuseppe,

Thanks for your answer, but I don't think that adding this route will duplicate the traffic, it will just redirect it right ?

I mean, for testing, I will need to reach the RP with multicast traffic on both side from the same router (multicast router)