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Multicast only fast reroute for ASR9000

Hello All

I am trying to see if MoFRR can provide the necessary level or redundancy for our network. Due to nature of the multicast service, we are looking into flow based MoFRR that is only available in ASR9K. We are running some initial tests but I am a little puzzled by the behaviour of flow based MoFRR especially when a multicast stream begins transmitting traffic.

To my understanding MoFRR chooses two RPF neighbours (primary / secondary RPF). For each multicast group it accepts the stream received through primary RPF neighbour and discards the one from the secondary. But as soon as ASR9K detects that a particular stream is no longer received through primary PRF path (the ASR9K seems to monitor the flow for the primary RPF path) it switches to secondary path. After that, the ASR
will start monitoring the flow on secondary path and it will revert back to the primary in case of an error.

The problem is when the stream starts, then if due to a problem (e.g. in an interface of the source stops working) traffic is successfully received only through the secondary path, then ASR will discard it, thus offering no redundancy (it seems as if ASR9K only monitors flows received along primary path and does not take into account if the stream is received through the secondary).  

Is there a way using flow based MoFRR in ASR9K to make sure that the ASR will forward traffic that it initially received only through secondary RPF interface?

Victor

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Hi Victor,

Hi Victor,

You may have already found an explanation or fix for this, but here is my input.

Try to test with RIB based instead of flow based, however be aware that RIB based may not be supported on ASR, even if CLI shows it as an option.

HTH

/Cisco Lad

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