OLC Reject for audio codec in a H.323-SIP B2B call involving CUCM & Expressways

[majeed002]

In the setup, CUCM is the centralized call controller and expressways are used for firewall traversal.  CUCM & expressways are correctly as per the Cisco document.  A SIP call from a public internet endpoint to CUCM registered MX300 G2 is successfully connected with video & audio.  But a H.323 call from public internet endpoint to the MX300 G2 in CUCM is failing.  It is seen in the logs that there is a OpenLogicalChannel reject for the audio codec.  I tried with both G711 & G729 from the public endpoint, but the result is the same.  Has anyone here faced similar problems.  Is there anything that I have look at.  Thanks in advance.
 

[Martin Koch]

Do you use encryption? Does it still behave like that if you handle the call unencrypted in your

expressway and cucm setup?

I would also check your (or the firewall for the remote setup) if there is anything messing with the h323 signaling (nat helper, inspection, l3gw, alg, ...)

[majeed002]

Hi Martin,

Thanks for the response.  I can look at the firewall.  But I would like to understand how does firewall can be a factor here when there is a clear OLC Reject.  Is it not confirms that the packets are indeed received and there are some issues in opening the logical channel. 

As firewall is not in my scope, I need to make clear reason for the other team to look at.

Thanks.