Remote Extensions with IPSec VPN




I have an issue and I need your help to understand and solve it

  • I have two sites with IPsec site-to-site VPN through two FortiGate devices (All subnets are connected through the tunnel)
  • I have a UCM6510 PBX in site A and GXP1615 extensions in site B
  • I need to connect the site B extensions to site A PBX by the local subnets, So the two sites can communicate through one PBX placed in site A

Problem (Solved):
at site B, I couldn’t ping the PBX or open the web GUI
And I discovered that the VPN tunnel was configured without NAT, So I created FortiGate roles to enable the NAT when communicating with the PBX subnets, And the PBX is finally pinging and opening GUI normally.

Main problem:
I have failed to register site B extensions to site A PBX through the local subnets (VPN tunnel), And I think there is no reachability between the PBX and remote extensions IPs.

Thank you in advance