My Client have 5 Locations ( offices and homes )
All locations DON'T have a static or public or dynamic IP (all location only have 172 . 22 . xx . xx )
All location have internet , offices have Professional firewalls , homes have simple wifi routers
In his main office he has 5 Grandstream (GS) phones and one GS UCM-6100 IP PBX machine.
I think the solution would be to setup a very tiny and inexpensive online hosted VPN server to make all locations able to connect to this Online VPN to start to see the UCM-6100 as if it were on the same lan , and Phones over 3G connections must be able to connect also.
2 Home have a simple wifi routers that may not have the VPN feature , what to do ?
Don't tell me about yourself , Only tell me how you plan to do it, topology and feasibility ?
I suggest : 2 hours , 100$