1. Login to the FortiGate and go to VPN -> IPsec Tunnels, then select "Create New"
2. Start off using the Site-to-Site configuration, this will automatically create Static Routes and Policys for you.
3.
Enter the IP address of your Telin hosted PBX.
Outgoing interface with be the WAN link you want to use.
Authentication Method will be Pre-Shared Key
4.
Local Interface will be the LAN connection you want the phones on.
Local Subnet of the phone
Remote Subnet will be provided on from Telin
5. Once created, edit the tunnel and click "Convert to Custom Tunnel" this will allow us to edit the additional fields.
6. goto edit "Phase 1 Propasal" and change the encryption, authentication, Diffie-Hellman Group and Key Lifetime to the Telin provided setup.
7. Do the same thing for Phase 2.
Once all steps are complete you will have registered your IPsec tunnel with your Telin phone system and can now start to provision your phones!
Please note some settings may change locations or looks based on FortiGate firmware.