I try to make G.729 calls with Nortel Softphone over VPN and firewall and it's curious but voice drops after a few seconds while signalisation still good. After 1 minute with no voice the softphone application crashes. If I use G.711 codec I have no problem at all.
All ports to be opened are opened. Ports are the same when using G.711 or G.729 or whatever the codec is.
Softphone <---> VPN concentrator <---> PIX515 <---> IPBX
When using G.711 we have no logs on the PIX515. It's ok all is working fine.
When using G.729 at the time the voice drops we have a few lines of logs like this :
Deny udp src inside:@ip ipbx/5210 dst outside:@ip softphone/5200 by access-group "acl_outside"
5210 and 5200 are RTP ports.
I don't understand because if using G.711 with the same PIX configuration and access lists it doesn't block the call. No such logs.
I have already created another access-list to allow the ports indicated on the logs. Now I don't have any more logs with G.729 calls but voice stills droping after a few seconds...
Any ideas ?