NAT Behavior on Dual ISP
Currently, I have a FortiGate configured with two ISPs, with WAN1 as the primary connection and WAN2 as the secondary connection.
For the LAN-to-Internet policy, I have a fixed IP pool NAT configured using the usable IP provided by WAN1. When I introduced an additional IP pool NAT on the LAN-to-Internet policies using the WAN2 Interface IP, users reported that they were unable to access the internet.
After reverting the change and removing the WAN2 IP pool, internet connectivity was immediately restored for the users.
My question would be:
- What is the recommended NAT design for a FortiGate with DUAL ISP connectivity when an existing IP pool nat is already in use?
- Are there known considerations or limitations when using fixed IP pool NAT address in a multi-WAN deployent?
- Are there any FortiGate best practices for maintaining internet connectivity while introducing NAT rules in a dual ISP environment?