Just checking to see if anyone else has run into this. We have a customer that is currently using sip trunks through broadvox. Whenever they set their extensions to forward all to an outside number, the call comes in on the sip, back out on the sip but no audio will pass? Any ideas?

More information needed. If it's a v4.40 or later system, i'd try disabling the MPS service within the IT Tool - menu 2.1.5

I'll check into that.

system is a 7400 with 4.51 software.
2 OAS cards both v2.01

20 sip trunks, with tandem trunking from 4 other remote locations.

You need to specify either a different public ip or different public and local port's for the MGI and MPS (if enabled) services for each OAS card.

EG
OAS1 local and public port for MGI 30000-30031, MPS 40000-40127

OAS2 local and public port for MGI 30032-30063, MPS 40128-40255

Also make sure that all your port forwards setup correctly.

changing the local port range on the MGI will require a system reboot.

Are you using Digital or IP handsets?