[Asterisk-Users] Handling SIP clients behind NAT on a semi-dynamic IP

[Chris Bagnall]

Greetings all,

A couple of clients have recently decided they'd like extensions to their
office PBXs at their homes, so they've duly been provided with preconfigured
phones which register with the Asterisk server at their offices (public IPs)
quite happily.

Every 3-5 days it seems that these remote extensions lose their registration
and are no longer accessible from the asterisk server. In all cases,
power-cycling the phone solves the problem immediately by forcing the phone
to re-register with the correct IP. The users in question have ADSL in their
homes with a standard consumer router (Netgear DG834), on a semi-dynamic IP
(it changes every few days, or whenever the connection drops and
reconnects).

>From that point on, there are lots of entries in the logs as follows:
 chan_sip.c: Got 200 OK on REGISTER that isn't a register

So I guess what's happening is the external IP is changing but the phone
doesn't know, and it's religiously sending its refresh signals every x
seconds to the asterisk server.

The remote extensions are all defined with nat=yes in sip.conf

Any way to fix this (short of telling the clients they need a static IP) ?

Thanks in advance.

Regards,

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