PIM Sparse Question

[chrisayres]

Hi,

A quick question

How often are register messages sent to the RP from the DR if the RP has no recievers for the group.

[Peter Paluch]

Hello,

I am afraid your question is not clear. A PIM Register message is used to encapsulate a multicast packet into a new unicast packet and tunnel it across a network towards the RP, until a source tree can be built between the DR and the RP. Each received multicast packet is encapsulated in a single PIM Register message, thus the frequency of sending PIM Register messages is directly related to the frequency of incoming multicast packets.

Does this answer your question, or did you perhaps wanted to ask about a different PIM message?

Best regards,

Peter

[chrisayres]

Not really, but I found the answer, after the router directly connected to the source receieves a register stop message it sets a 1 minute suppression timer and sends a null message 5 seconds before this expires. If the RP doesn't reply to this the source router then sends another register message.

Thanks anyway

[Peter Paluch]

Hello,

Thanks for updating! Yes, you are right I focused myself on the PIM Register process without taking into account the fact that if RP has no joined receivers, it will send a PIM Register-Stop to the DR. Thanks!

Best regards,

Peter

[cbeswick]

Hi Guys,

I have a multicast issue which you may be able to help with.

We use auto rp, with all routed interfaces configured to use sparse-dense-mode.

We have a situation at the moment where more or less every S,G entry is stuck with the register flag.

I can see that the *,G entry has stopped on the DR and that the S,G entry has joined the SPT with the T flag. But it also displays F for registering.

I have carried out some debugging on both the DR and the RP and can see that the register stop is being sent by the RP and the DR is receiving the register stop, however the DR keeps sending the register messages for all multicast traffic.

I am concerned that excessive multicast traffic will from our CCTV system will eventually result in some CPU issue on the DR.

All traffic from the RP  (which sits on the core switch) down to the receiver looks perfectly fine.

I am trying to understand why the DR is stuck in register mode even though it has joined the SPT.