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Simon Battye

Routing PSTN Calls via CUCM / VCS+CUCM Int


I'm having problems routing PSTN based calls via CUCM, here is an overview of current configuration:

  • VCS / CUCM Integration already complete and tested working between EP's and CTS devices;
  • Extra search rule configured to match outbound PSTN numbers, and resolve against CUCM accordingly ** (9{1}[0-9]{11})@domain(.*) **
  • Locate tool on CVS resolves PSTN numbers against CUCM SIP Trunk
  • Outbound PSTN access is configured within CUCM with a VG, CTS endpoints can dial out to PSTN as part of this configuration
  • All CSS and PT configueration is OK.

So, currently i can't dial out to a PSTN number from a video endpoint registered to the VCS, but i can dial a CTS registered to CUCM. When attempting to dial a PSTN number, the calls drops straight away, search history on the VCS shows that the request was matched against the CUCM SIP Trunk, outbound alias is {PSTN}@{CUCM-IP}; but displays a reson code of 'Bad Request'.

I've used DNA in CUCM to ensure CSS and PT's aren't causing the problem, everything  can route OK.

Has anyone come across this problem before....??


Michael Boscia

Can you give us more info about your setup?
Are your endpoints dual registered with SIP and H.323?
Is interworking turned on?
Are you using traversal/interworking to make this call work?
What protocols are available on the neighbor zone between VCS and CUCM?
Can you ping from VCS endpoint to CUCM, and from that endpoint to your voice gateway, or whatever is terminating the call on the PSTN?

Sent from Cisco Technical Support iPhone App


Thanks for replying, please see responses below:

  • Endpoints are dual registered as SIP and H323
  • Interworking setting is configured as 'on'
  • I've attempted these calls as SIP to SIP and H323 to SIP using interworking, same result. SIP-SIP and interworking calls work from VCS endpoint to CTS registered to CUCM
  • It's a SIP trunk configured between VCS and CUCM, search rules/transforms are configured accordingly to accommodate the alias manipulation i.e. presenting alias as {DN}@{CUCM-IP}, as opposed to {DN}@{DOMAIN}. SIP is the only protocol configured (using TCP), H323 is switched off.
  • Endpoints can ping both the CUCM Pub and Voice Gateway registered to CUCM, VCS can also ping these devices.

I hope this helps? Apart from the search history returning the search as a 'bad request', i haven't had chance to get traces, hopefully i'll be able to get these soon.


Hi Simon

What about VCS call history (view)?

Can you attach traces from CUCM? What version of VCS and CUCM you have?

Also please capture screenshot of trunk, PSTN gateway and route patter configuration.




Under VCS Call History, i see the following happening:

- Call Status: Connection Failed

- Disconnect Reason: 400 Bad Request

- Duration: 2 Seconds

- Protocol: SIP -> SIP

I am running VCS X7.2 and CUCM version 8.6.2.

Which section of the trunk are you interested in looking at, i'll see if i can get the right info in one screencap, also the route pattern is: 907XXXXXXXXX, routed to the PSTN GW.


Simon Battye


This has now been resolved.

The PSTN Gateway associated with CUCM was rejecting the calls due to an invalid source address. Endpoints initiating PSTN calls where C series codecs registered to VCS as the following SIP URI: - CUCM was presenting the source address to the PSTN Gateway as: ; this needed to be presented as numerical format in order for it to be valid.


What did you do to resolve I'm having the same issue ,but when I create a transform to send just the number I get a bad SIP URI error on the VCS.

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