[Asterisk-Users] Remote employees using Polycom 501 lose ability to receive incoming calls after few minutes.

[Von L.]

Hello,

Here is a breakdown of the issue I am experiencing. I have three remote
employees, in various states, who have Polycom 501 phones. They are
unable to receive incoming calls after a few minutes of the phones being
plugged in. They work immediately after being plugged in, but they lose
the ability shortly thereafter. They can always make outbound calls, but
only to real phone numbers, not extensions.

They each have NAT routers, and I have triple checked that they have
opened/forwarded the correct ports, basically 5060-30000 UDP. Once they
plug the phone it (power and ethernet) I see on the CLI console of the
asterisk server that the phones register:

Asterisk CVS-v1-0-12/01/04-18:46:01, Copyright (C) 1999-2004 Digium.
Written by Mark Spencer <markster at digium.com>
=========================================================================
Connected to Asterisk CVS-v1-0-12/01/04-18:46:01 currently running on
bell (pid = 3652)
nell*CLI>
Verbosity is at least 10
-- Registered SIP '3015' at XXX.XXX.XXX.XXX port 1500 expires 3600

Here is the top part of my sip.conf

;_____________________________________________________________
;sip.conf
;_____________________________________________________________

[general]
port=5060
bindaddr=0.0.0.0
externip=XXX.XXX.XXX.XXX
localnet=XXX.XXX.XXX.XXX/255.255.255.248
canreinvite=no
tos=reliability
srvlookup=yes
disallow=all
allow=ulaw
dtmfmode=rfc2833
nat=yes
ignoreregexpire=yes

I know it has something to do with the NAT because if I plug my Polycom
directly into my cable modem, thus making it sit on the Internet and
have a real IP, everything works just fine.

I am curious what I am missing.

Thanks.

Von L.