CUCM 9.1 - Region issues between SBC and H323 Gateways

[Jonathan Hay]

We are in the process of converting remote locations to centralized SIP trunks and also converting the remote location gateways to H.323 for faxing. I have had an issue with the last 2 locations not using G711 between the SIP trunk and the remote H323 gateway. Here is the setup of the regions:

G729 Region - Assigned to SIP Trunk device pools so that it will communicate G729 to remote location phones.

G711 Region - Assigned to H323 device pools so that it will communicate G711 to remote fax machines (FXS Ports on H323 GW).

I have double-verified the region relationships. 

So far, the 15 locations that have been converted are working as expected but the last two locations refuse to use G711 for communication to the H323 GW. In order to resolve the issue, I had to place the H323 GW in the same region as the SIP Trunks. The other location that refused to communicate over G711 was a VG224 device and I also had to place it in the same region as the SIP Trunks. 

I am really not sure where to start on troubleshooting since all of the other locations are working as expected. How can I troubleshoot the region relationship to make sure the SIP Trunk and H323 gateway are using the correct region? 

[Chris Deren]

What is the codec between these 2 regions? What is the codec/codec class on the voip dial-peer on the H323 GW?

[Jonathan Hay]

The codec between the 2 regions is G711 and the codec on the dial-peer is G711 as well. 

[Chris Deren]

Can you post relevant CUBE and H323 configs?  Point out the number used.

[Jonathan Hay]

The SBC's are Acme Packet devices. 

I should have mentioned this earlier but sending a fax works like a champ. The dial-peer specifies g711 in the codec and it works every time. The problem is receiving a fax (a fax inbound from the SIP trunks) That is when it is trying to use G729 even though the region relationship specifies G711. 

Here is the region that the H323 gateways use (G711_REG). The SIP Trunks use the G729_REG. 

[Chris Deren]

Region specifies maximum codec that can be negotiated, so when you have G711 it does not prevent G729 from being negotiated. Sounds to me like you are either missing incoming dial-peer on the H323 or using incorrect one. A call has 2 call legs on the GW, each matches a dial peer, if there is no incoming dial-peer i.e. with "incoming called-number ." default dial-peer 0 will be used which is hard coded for G729. Add this command to you dial-peer with G711 codec defined.

[Jonathan Hay]

Ah okay. Here is the config on the H323 router:

dial-peer voice 100 voip
 preference 1
 destination-pattern [2-9]..[2-9]......
 modem passthrough nse codec g711ulaw
 session target ipv4:X.X.X.X
 incoming called-number .
 dtmf-relay h245-alphanumeric
 codec g711ulaw
 fax protocol pass-through g711ulaw
 ip qos dscp cs3 signaling
 no vad
!
dial-peer voice 300 voip
 preference 3
 destination-pattern [2-9]..[2-9]......
 modem passthrough nse codec g711ulaw
 session target ipv4:X.X.X.X
 incoming called-number .
 dtmf-relay h245-alphanumeric
 codec g711ulaw
 fax protocol pass-through g711ulaw
 ip qos dscp cs3 signaling
 no vad
!
dial-peer voice 200 voip
 preference 2
 destination-pattern [2-9]..[2-9]......
 modem passthrough nse codec g711ulaw
 session target ipv4:X.X.X.X
 incoming called-number .
 dtmf-relay h245-alphanumeric
 codec g711ulaw
 fax protocol pass-through g711ulaw
 ip qos dscp cs3 signaling
 no vad
!
dial-peer voice 10 pots
 service default
 destination-pattern 5122365078
 port 0/1/0
!

[kelvin.blair]

Can you run the following debugs:

debug voip dialpeer inout

debug voip ccapi inout

Make a test call and post the output. This will help identify the dial peers being use as well as other relative information to troubleshoot the issue.

Thanks!