Multicast over DMVPN

[aacole]

I'm working on a network to support VHF radios transceivers. The backbone uses DMVPN, and requires Multicast for base station discovery and replication of voice traffic between base stations connected to the DMVPN.

Each base acts as both a Mutlicast source and receiver, I'm trying to figure out how best to set up the network to support this requirement.

Any guidance gratefully received!

The DMVPN is up and working, unicast flows are operational. Its optimal set up of the Multicast I'm not clear on.

Andy

[francisco.trigo]

Hi Andy!

Are you using loopback int for this?

I'm using only Vif1 with a /30 mask, you set this like it?

peer to peer gre mode in the same lan works, in internet do not but the tunnels are up and ping including the remotes vif1.

I'm a little bit lost..

[nsti_0682]

So whats the verdict...does iWAN (DMVPN) support multicast sources at spokes where the destinations are at other spokes? It sounds like the answer is no?

[aacole]

Yes, DMVPN does support the use of multicast sources behind spokes.

Set the RP to be at the hub site, set PIM so that the hub becomes the DR.

All replication takes place at the hub. I have this working now, with multicast sources and receivers behind each DMVPN node.

[aacole]

Hi Yes, I have it working. I tried to reply from my phone, but it seems my reply never got uploaded.

I set the RP (static) on the one hub I have. Each spoke has a static entry for the hub RP address. Each link is using PIM sparse mode and IGMP v3 on the LAN facing interfaces.

On the hub tunnel interface set:

ip pim dr-priority 2

ip pim nbma-mode

on the spoke tunnel interfaces set:

ip pim dr-priority 0

ip pim nbma-mode

If your multicast source is behind the hub then this should work. If you have multicast sources behind spokes (as I have) then you need to set the following, only on the spoke routers:

ip pim spt-threshold infinity.

This command forces the spoke to spoke multicast traffic to stay on the shared path back towards the RP at the hub, the hub router then replicates this traffic back to the destination spoke which has requested to join the stream.

Andy

[francisco.trigo]

Hi Andy!

Thank you for your response!

I'm think that we have the same config. Each spoke is the LMR device and the hub is a LMR device too but is defined like the LMR server.

You use OSPF as multicast with thw Vif1 address and tunnel address to rigth?

Best Regards

Frank

[Philip D'Ath]

I haven't done multicast over DMVPN, so are not sure.

Did you follow the multicast portion of the guide I posted a link to?

[secureitgroup]

I had this same exact issue, I had my multicast working in a non-dmvpn LAB but after moving into a production network with DMVPN it was not working.  For me the fix was adding the following on the DMVPN Hub Router.

ip pim nbma-mode

I guess the other big thing that stands out in my multicast labbing is that you need to be ABSOLUTELY sure your multicast stream is not being sent out with a ttl=1.  My multicast test was to use VLC and it sets the TTL to 1 by default so it was dying at hop 1.  Figured I would add this as it caused me many hours of frustration.

[MHM Cisco World]

make new post, let all see your issue and reply 
MHM