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Multicast - RP losing sync with distribution router


Part of my security cameras are on my IP network. The camera a sending a unicast flow to the archiving server and a multicast flow for the real time viewer.

Problem is overtime, multicast entry is deleted from the RP source table. In this case, the RP is a core6509. The distribution router always keep the entry but there is no refresh

Question : Is there any timeout for multicast session entry in the RP. Is there a way to refresh the RP table whitout clearing the mroute entry in the distribution router


Re: Multicast - RP losing sync with distribution router

Hi there,

There are a few ways that you can keep a multicast entry alive, but the all revolve around having some multicast traffic.

I would configure the router closest to the real time viewer to be permanently in the multicast group. There is an interface command "ip icmp join-group 239.x.x.x", this will make sure that the flow is always passed through to the router.

Also, to keep the flow alive, you can set a router (here I would use the one closest to the ip camera) to poll the 239.x.x.x address, thus creating the multicast traffic.

You can do this in 2 ways, either by setting the ip sla monitor to ping the multicast group every minute or so, or have a kron job do it. Personally, I would use the ip sla monitor,as I've never really had much joy with the kron scheduler.

Check out this link for more details:-

Basically, you'll be keeping the multicast stream alive between the router that connects to the camera and the router that connects to the viewer.

Have a go and let me know how it goes!

Best Regards,


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