CUCM 11.5 to FreePBX SNG7 Trunking

I’m trying to set up trunking between the CUCM 11.5 and FreePBX SNG7 call managers in my lab. I’ve been through Google and found various answers that don’t work. Currently I can ring the Cisco phones from FreePBX, but get “all circuits are busy” error when I pick up. Going the other way, Cisco won’t even try to dial even though I’m pretty sure the call routing is set up properly.

Does anyone have a good “How-To” or configuration/set up instruction that I can try? I’ve done so many changes that I think I’ll need to check everything to get it working.

Thanks in advance!


Tell us a little more about what you’re trying to do.

For example, are you trying to add a FreePBX node to your network to handle a few phones? Do any of your calls work? It sounds like the SIP part might be working, but the RTP routing might be hosed.
Are you going to replace your CUCM system with FreePBX? Have you looked into Chan-SCCP-B for your phone channel driver?

Sure thing.

I teach telephone system security and each call manager represents a different site. I’m trying to get them trunked together so students can check them against policy - sometimes you have to use a TDM trunk, sometimes an IP trunk is allowed. I have two FreePBX VMs up and running and talking to each other over SIP trunks. I’m trying to add the CUCM instance to the mix, but I can’t find a good guide to get them all talking.

I have not looked into Chan-SCCP-B, I’ll do some research on that. All my Cisco phones are SIP phones though - will that matter?

Chan-SCCP-B is designed to add an actively developed “Skinny” stack to the list of channel drivers. If you aren’t using any Skinny phones, it’s probably overkill, although the system does support a phone phones that are SIP-Only from the Cisco line.

I haven’t looked at CUCM since the name change, so I can’t tell you exactly how to do it, but in general the steps for connecting it to any SIP provider should be about the same as connecting up a FreePBX instance. Set up your SIP trunks (on each FreePBX instance and on the CUCM instance) to point at one another and use IP-based authentication (unless you’re trying to allow the students to hack the systems).

Even then, the Integrated Firewall is going to get in your way on the FreePBX side. There are also NAT considerations that you may or may not have to deal with - that depends largely on your network architecture and what addressing scheme(s) you are using within the lab network.

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