Registering phones from another subnet

I am working at a site with a Trixbox CE, the operations manager has already approved us transitioning to a FreePBX but for the time being we are trying to register phones across a VPN. the trixbox is on a 192.168.1.x network and there are phones on that network currently registered, we are trying to add phones to the 192.168.2.x network but we get one way audio, I believe we need to edit our sip.conf file

here what is in it now
externip=pbx.ouroffice.com
localnet=192.168.1.200/255.255.255.0

I was going to add this line below the one that says localnet=

localnet=192.168.2.0/255.255.255.0

is this the correct way to remedy the issue? Any help would be great

Yes but you can (and should be) doing that all through the GUI in Asterisk SIP Settings

Yes, that’s the correct way to address the issue, but you should also be able to do it from the Asterisk SIP Settings Module. I’m pretty sure that Trixbox CE had that module…