incoming calls from h323 gateway not working

[Mohammed Idris]

PSTN---VG-H323---MPLS---CUCM

Incoming call from PSTN not working. Outgoing is fine. Please find the file attached with config and debugs.

[Vivek Batra · Accepted solution]

Can you please remove the command viz *no call fallback active* and check if that is the cause of call failure...

Thanks

Vivek

[Mohammed al Baqari]

Looking at your ISDN q931 debugs, I can see that your call is looping back to the telco. The call is coming to number 966 and is looping back to telco as 6966 (which is matching your incoming translation profile).

This implies to me that VG is trying to contact CUCM using both VoIP dialpeers and this is failing. The last resort is go out of the POTS dialpeer (.T).

Please do the following:

1. From VG try to ping CUCM (ping 10.147.5.5 so g0/1 & ping 10.147.5.6 so g0/1)

2. From VG try to telnet to CUCM one H323 port (telnet 10.147.5.5 1720 /source g0/1 & telnet 10.147.5.6 1720 /source g0/1)

3. If both steps are successful, share the following outputs:

debug cch323 h225

debug voice dialpeer all

CUCM H323 configuration

[Mohammed Idris]

Thanks Vivek, it worked like charm !!. But why it worked after removing the command. Though that command is part of SRST config. Please explian if you can. Or refer to me some link.

[Vivek Batra]

I have never came across this command in any of my setup including SRST however got following reference similar to yours;

https://supportforums.cisco.com/discussion/11458611/h323-dropped-calls-isdn-q931-quality-service-not-available

Will try to go inside the root cause and update you once I have any findings on the subject.

[Mohammed al Baqari]

This command is used to failover from VoIP to PSTN in case of network congestion (jitter, packet loss, latency). As I mentioned you have a problem between your VG and CUCM which is causing loop back to PSTN.

When you removed this command, the calls started going through but with degraded quality.