We've got a SPA2102 installed behind a client's very, very restrictive firewall. They block all outgoing ports by default.
We've had them add rules to allow SIP traffic on 5060 and the default RTP port range of 16384 to 16482.
This all works just perfectly and calls in and work as expected.
However, faxes fail every time. In looking at the firewall rules it appears the SPA2102 is sending T.38 packets over very different port numbers and they are being blocked. In our tests we saw sessions on ports 4242, 4671 and 4899 so it looks like the range if pretty broad.
My questions are:
1) What range of addresses will be used for T.38
2) Is it possible to change that range to a smaller one so we can have them open those ports in the firewall. Since the SPA2102 can only do one T.38 session at a time I wouldn't think the range need be all that large.
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