[Asterisk-Users] PSTN Incoming call on real line disrupts VoIP call over DSL circuit

[Hadar Pedhazur]

Rich Adamson wrote:
> Hadar Pedhazur wrote:
>> Jerry Jones wrote:
>>> I would guess either the DSL itself is bad or perhaps the dsl Modem. 
>>> perhaps calling Bellsouth would be helpful? Does other Internet 
>>> traffic get interrupted also?
>>
>> The rest of the Internet traffic is _not_ interrupted, and his voice 
>> continues to be heard, so even that part of the connection continues 
>> uninterrupted.
>>
>> I'm not sure how to diagnose whether the modem is bad or not, given 
>> that other traffic (and half of this traffic) continues to flow over 
>> it. I can only imagine calling Bellsouth and being told "we don't 
>> support VoIP unless you buy our VoIP service...".
> 
> Not likely to be a bad modem. More likely is something like NAT tables 
> getting in the way (eg, firewall, nat box, or whatever).
> 
> If its just your voice that "he" can't hear, its likely to be the 
> firewall/nat box on his end as "it" doesn't know which udp port the 
> inbound rtp traffic is going to use.

It definitely feels like that's what's happening, but it seems strange 
that it's kicked off by an incoming POTS call. What would make the 
firewall change what it thinks it's talking to already?