[Asterisk-Users] SIP Phones behind dynamic IPs

[Chris Bagnall]

Greetings list,

I'm coming across an issue with some of the GXP-2000 phones we have out in
the wild at clients' employees' homes. In most cases they're behind consumer
ADSL NAT routers on a dynamic IP from their ISP.

In a nutshell, the phone is unable to be called unless it's restarted first,
after which it's fine for a good few hours, then it stops working until
restarted again.

The problem doesn't seem to be anywhere near as regular with users that are
on cable connections (these tend to have much more "sticky" IP addresses -
they change only every few months rather than every time the ADSL router
connects), and non-existent on ADSL connections with static IPs.

I've tried various permutations - with STUN, without STUN, NAT keep-alives
down as low as 10 seconds, nat=yes in sip.conf, ports forwarded to the
phone, ports *not* forwarded to the phone, etc.

I think what's happening is that the ADSL router is reconnecting after a
break in the connection (as it should), getting a different IP, but the
phones don't seem to be recognising they've got a different IP and updating
the asterisk server with the good news.

Has anyone else encountered similar issues? Anything else I can try (bearing
in mind I have no control over the ADSL connections the users are subscribed
to)?

Thanks in advance.

Regards,

Chris
-- 
C.M. Bagnall, Director, Minotaur I.T. Limited
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