UCM6202 - Ringing but no audio in external



I can’t configure my IPBX to run outside LAN.
When i’m not in the lan and i make a call the sip exchange works fine but my computer send audio to private adresse of UCM…
I looked in the SIP packet and for i think that the UCM send his private IP instead of Domain Name or public IP…
I entered the Domain name in all the field that requires it…

Can you help me to configure that ?

Best regards,


Look at the flow of a call in your trace and then open up the INVITE. Open up the headers within the INVITE and look at the contact and connect headers. The IPs within will show what the device that sent the INVITE is telling the other device to use in its messaging to setup the call.

Look at the 200OK for the same call and open up as above and again look for the contact and connect headers as this is the other device telling the other device to use when communicating back,

What you are showing is not related to a call per se, it is a Notify message. The line just above it is the 200OK and the INVITE is above the 180 Ringing message.


Thanks for your answer.
As you can see below the field “from” is good but the field contact told private ip of ucm…


Don’t care about the from field, that field is typically used to show who is calling (Caller ID)

Care about the CONTACT which is showing a private IP.

In the PBX settings, SIP settings, NAT

  1. In external host input your FQDN (resolves to public IP) or your public IP
  2. In the SDP box below external host, enable (check) it.
  3. In the section below for local network, please enter your local lan info.
  4. In the UCM extension settings, enable NAT for the extension that will be remote.
  5. DO a backup of the system
  6. Upgrade to the latest 9.127 release for the UCM
  7. Insure that any SIP ALG is disabled in the router.

The above only addresses the UCM side, there is more to do with the remote.


All your point were done except the upgrade.
I’m running
I will do this backup and upgrade then keep you inform.
Thank you again