| Description |
This article describes how the SD-WAN rule selects the interface to be used when employing the manual interface selection strategy. |
| Scope | FortiGate. |
| Solution |
On FortiGate, PORT 1 and PORT 2 will function as ISP providers, along with PORT 3, designated for LAN traffic.
PORT 1 - 10.47.2.32. PORT2 - 10.47.18.32. Test Machine IP – 10.119.3.61.
Here is the SD-WAN Rule setup.
Since PORT1 is ranked higher in interface preference than PORT2, the anticipated behavior is that the SD-WAN Rule, upon activation, will utilize PORT1 to route the traffic from 10.119.3.61 destined for the internet.
Now, if it were in the PORT 2 position, above PORT 1 in the interface preference of the SD-WAN Rule, the expected behavior would involve PORT 2 being employed to perform NAT for the outgoing internet traffic.
Here is the forward traffic log that would show that PORT 2 is used to translate the traffic going out.
Now, if port 2 goes down, despite its higher position relative to PORT 1, PORT 1 will be utilized to perform NAT for outgoing traffic.
To test this, PORT 2 has been disabled.
Here is the screenshot that would show PORT 1 IP is used for NAT traffic going out.
Additional information: To include zone preference in addition to interface preference, the scenario unfolds as follows: Interface preference will supersede zone preference. The same underlying logic applies to zone preference, where the topmost interface is chosen for NATting the traffic.
For example:
The SD-WAN rule prefers the interfaces in the following order:
Related documents: Fields for configuring WAN intelligence |
