Multiple Sites with NBX & Multicast Routing?

[slebbon]

We have a number of (remote) office sites with their own 3com NBX 100 systems. We also have a 3com NBX 100 system at the local (main) site. Right now the sites are connected via Cisco DMVPN tunnels (all IP traffic allowed), and all Cisco routers currently do NOT have Multicast routing enabled. Right now each site's NBX systems operate independently, however they do use some VTL's to communicate calls between the offices (this traffic flows over the DMVPN tunnels just fine).

We also would like to have some remote sites that do NOT contain their own NBX systems to have phones tied into to 1 of the NBX systems. This works with the most basic phone features, but all phone features requiring multicast don't work (as expected, since multicast traffic is restricted to each local office's network due to no router path to let it get out). In order to enable some of those remote offices without NBX systems to use multicast, it would seem we'd have to enable ip multicast on the ciso routers, at least in the main office housing the NCP we want to tie phones into, and the remote office without an NCP. Our concern however is that multicast traffic from one office with an NCP will 'leak' into other office networks that have NCPs as well. We can only imagine that this would be a 'bad thing'.

What can we do about this? Anyone have suggestions how to configure the routers to get this to work as we want? Are there any other approaches we should look at? Other options?

Thank you.

 

[curtismo]

I'm also interested in hearing a solution, as I have a similar issue. We have several NBX 100 systems at sites on a Metro Ethernet network, with each site having a Layer 3 routing switch. When we added a site recently we purchased a switch that does not have DVMRP (all the rest do) and all the rest of the sites now cannot establish conference calls with this one site on VTLs.

 

[douglasDavenport]

http://www.nbxmulticast.com/

These guys wrote a simple program to turn the status multicasts into unicasts so they will go over your WAN. I don't think it will work for paging but most features like status lights and time display will work at remote sites.

 

[slebbon]

Ya, I've seen that; but even on their site they write:
"...the NBX uses Multicast Groups, which are only fully supported by the most expensive routers and VPNs.

When our small company was faced with the prospect of spending a ton of money on IGMP Multicast capable routers to fix this, we decided that we could easily write a small program to tunnel the NBX’s multicasts to a different network."

In our case, we've already spent a "ton of money on IGMP Multicast capable routers", and we'd just like to USE them. The problem I'm running into is really finding out what will happen on the 3com side of things...with our multiple NCPs?

Also, we don't want to have to bother with having software running on server(s) at both local and remote sites, because it would just introduce another point of failure into the phone system. As well, we would like to use some of the multicast-only features that the software tunneling solution still doesn't provide--such as Conference Calling support.

Is there no-one who knows how to setup interconnected sites with multiple NCPs?

 

[ashyti]

The alternative will be to build GRE tunnels accros the sites
If your routeers do not support that then you are out of luck

 

[slebbon]

Yes, This is what we already have GRE tunnels across the sites--that DO support Multicast traffic (although it's not yet turned ON. It's the Cisco DMVPN solution, which provides a Full-Mesh VPN tunnel connection between ALL Sites.

The question I have, and our big concern, is how will the 3com NBX respond, when suddenly it can 'see' other NBX NCP's inside it's own 'multicast domain'? What do we have to do to ensure the large site's NBX setups are unaffected, while allowing small sites without NBX setups to start receiving the necessary 3com multicast traffic?

 

[douglasDavenport]

There is so little good information out there regarding the NBX especially the multicasts and vlans. Good luck in your quest.

 

[KD7SYA]

You can change each NBX's multicast IP addresses to unique ones, so the NBX's don't get confused with each others multicast addresses. I would think this would solve the problem of NBX confusion in a multisite configuration.

 

[slebbon]

Will changing the IP Multicast addresses in use by each NBX cause any issues for the phones themselves? How do the phones know what Multicast addresses are set on the NBX?