Hi,
I have about 50 extensions, however some seem to go offline periodically. If I reboot the phone they come back, then a little while they go offline again, or on 4 line phones sometimes only line1 will work.
Any idea to fix this?
TIA
NAT related maybe? Static IP or DHCP?
It uses DHCP, private IP address, in the freePBX interface for the extension I have nat set to yes.
Turn off NAT on the extensions and try again.
Really, you should only use NAT if your extensions are remote or behind a router. I have all mine set to NO - RFC3581 which has never failed me. None of my phones are on the other side of the router, they are the other side of the switch so do not require NAT translation.
Oh, they are remote, the pbx server is in a datacenter, and the extensions are at a separate office location.
I had trouble getting it to work before with nat off, and turning that on, seems to fix it, except for the extension going offline sometimes now.
In that case NAT should be required. Could be the DHCP updates knocking them out!? Not much experience with remotes, so I hope someone can step in and go from here.
Sorry, thought this was a local server.
My fault, I should have mentioned that.
Did you try using a STUN server setting on your equipment? Just a thought? Other then this I am stuck 
You need to tell us more about your setup.
Did it ever work?
What kind of firewall?
What kind of phones?
Have you considered using a point 2 point VPN?
If you really want assistance with this issue, you’ll need to provide a significantly greater amount of detail, and probably need to spend a bit more time troubleshooting.
What version of Asterisk? What version of FreePBX? What Distro?
What does the log show?