Need assistance - dual WAN

[ManUnderConstruction]

Hi,

Good day everyone.
I would like to seek your assistance as networking is the least of my professional skills :(

Currently, I need to transition the current Internet Line from existing different ISP to another one for one of our remote office but at the same time, let the other old Internet Connectivity up for the time-being.

The old Internet Line (A) is connected to WAN1 of the firewall, and has existing site to site VPN.
The new Internet Line (B) is connected to WAN2 of the firewall. The Internet Line (B) connection has it's own router and the PublicIP is NAT'ed to 192.168.1.2 - connected to WAN2 which now has 192.168.1.3 IP.

My question is, what is the best approach for this? I would like to set-up WAN2 (Line B) as the main line and also set-up site-to-site VPN but at the same time, retain the existing line A as the backup temporarily in case for 2 months before totally discontinuing it if all works well. ...

How can I do this? 

Thank you!!! 

FortiGate 

[Jackie_T]

Hi,

For simple setup, you can achieve this by configure ECMP routes.
Mean both WAN1 and WAN2 will have same distance value set, but WAN1 will have higher priority value set.
The link with higher priority value will be less preferred and stay as standby link.
If you need redundancy for VPN as well, you can configure monitor VPN2 for the VPN configured under WAN1.
In case VPN2 under WAN2 failed, then WAN1 VPN1 will come up.

Reference document:
For Dual WAN:
https://community.fortinet.com/t5/FortiGate/Technical-Tip-Redundant-Internet-connection-without-load...

For VPN:
https://community.fortinet.com/t5/FortiGate/Technical-Tip-IPsec-VPN-Site-to-Site-tunnel-monitor/ta-p...

Thanks.