Multicast Tunnel RPF Failure

[lagapidis (Lazarus Agapidis)]

Hello Miguel

First of all, remember that the mroute commands refer only to multicast traffic, so whether you implement the ip mroute 192.168.1.0 255.255.255.0 192.168.12.1 command or not will not affect the unicast traffic.

This command is implemented in order to verify that the RPF check is passed. The RPF check essentially checks to see if the source IP address of the multicast traffic is reachable via a routing entry in the routing table that matches the interface via which the packet entered the router. If this check is not passed, the packet is dropped. In order for this check to be passed, the ip mroute 192.168.1.0 255.255.255.0 192.168.12.1 command is implemented, thus satisfying the requirements of the check.

@mv.miguel.vieira

Then in R1 you don’t have any “ip mroute”. Should we also route the unicast traffic by the tunnel?

Once again, the mroute commands do not apply to unicast traffic. However, in order for unicast traffic to successfully traverse the tunnel, the appropriate routes must be installed in the routing table.

@mv.miguel.vieira

If we have a bidir multicast implementation with a GRE tunnel, would it work? But in that case my question about mroute in R1 would make sence, isn’t it?

Remember that the above command was implemented not to enable bidirectional multicast traffic, but to satisfy the RPF check. If the RPF check is satisfied, then multicast will function correctly over a GRE tunnel.

I hope this has been helpful!

Laz