TIP: Sophos UTM 9 - SIP functions don't work properly.

[localzuk]

So, after much faffing getting incoming SIP calls to work from our comms provider (outgoing calls to random numbers were completely silent), it turns out that the SIP functionality built into the Sophos UTM software doesn't seem to work properly.

 

It was randomly dropping the 183 Session Progress messages, amongst other things.

 

Turning it off, and putting in place traditional NAT rules instead worked a treat.