I have a Callmanager 4.1.3 and a 2811 gateway in the Madrid office, also we have two more office (Barcelona and Valencia) with gateways 2811 with SRST.
Madrid's gateway has two E1 PRI, one for calling to mobile phones and the other one for calling any other destinations. All offices call to mobile phone through the main office.
Barcelona and Valencia gateways have one E1 PRI to PSTN each.
All gateways are MGCP controlled.
Each office has 30 phones.
Barcelona and Madrid have a data link for voice of 512Kbps dedicated.
Valencia and Madrid have a data link for voice of 512Kbps dedicated.
Barcelona and Valencia have a data link for voice of 128Kbps dedicated.
Between offices the used codec is G729.
The problem is that when a person from Valencia call to mobile phone doesn't hear any tone but the call is established, you can see established in the phone LCD and the mobile phone ring but you can't hear anything in both ways. The person hangs up and redial the call is established successfully. This problem happen sometime, NOT ALWAYS, more or less 10% call to mobile phones from Valencia.
We don't have this problem when call from Barcelona or Madrid.
Thanks for your help.