I am running Asterisk 1.6.2.7 x86_64.
The phone in question is a Polycom Soundpoint 301 with SIP version 3.1.3.0439
Our main office, where the Asterisk server is connected to the internet via a Linksys RV042 local net is 192.168.1.0/24 the router’s local address is 192.168.1.254
Our remote office where the phone that I’m having the issue with is connected to the internet via a Linksys RV016 local net is
192.168.0.0/24 the router’s local address is 192.168.0.1
The two offices are joined via a gateway to gateway tunnel.
The remote office has a linux server running DHCP with option 66 and running an ftp server hosting the provisioning files for the phones.
The first time I configured the phone, it worked just fine for a few days then it wouldn’t register anymore.
After reformatting the phone, it came back up and worked for a few weeks, then wouldn’t register anymore, rebooting and reformatting did not work.
I provisioned another phone with the same settings, and then it worked for two days, then it wouldn’t register anymore.
In the sip.cfg, I have that extension configured to allow traffic from the remote office’s subnet.
The phone can place calls out, but will not ring. A packet capture of all the traffic to the asterisk server records RDP and SIP data for a calls placed by the phone, but no registration attempts. A user at that office confirms that the STATUS->LINES->LINE INFO on the phone’s menu has no registration, but has the correct ip address for the Server-1 field.
Sorry about the small novel, but this problem has been kicking my 
on and off for a couple of weeks now, and if anyone out there can help me, they are going to need a boatload of info.