fortigate sd-wan spillover

[AMINET]

Hello,

I have two static routes wan1 and wan2 to internet with same priority and distance, I enabled sdwan so ecmp will use implicit base algorithm sd wan, I choose the spillover  algorithm, my problem is how do I decide which interface to use first.

I noticed it picks the route with a smaller gateway to use as the first time and I can't edit it

Thanks,

[subramanis]

Hello AMINET,

The FortiGate will use the lowest numbered interface first

Example:

Port2 & Port3 in sdwan with Spillover, Port2 will be used as a primary member and port3 will be used once port2 reaches the spillover thresholds

If you add another member, port4 in Spillover then

>>> port2, Port3 & Port4

If you add port1 instead of port4 then

>>> port1, Port2 & Port3 <---b'coz port1 is the lowest numbered interface

https://community.fortinet.com/t5/FortiGate/Technical-Note-Dual-WAN-scenario-static-and-policy-route...

Thanks

Sasikumar.S

[FortiPlayer168]

Hello,

For wan1, HA1, DMZ and Port1 , which is the lowest numbered interface ?

[AMINET]

hi @subramanis 

thanks for your reply, the documentation says that the highest route in the routing table will be chosen, in my case the highest route in the table is not the one with the lowest port number (I have tested).
so the Spillover don't always choose the one with lower port number as primary
we are looking for the method to control it.

thanks in advance..

[subramanis]

Hi AMINET,

What you mean highest route? Can you share the routing table and sdwan configuration?

Thanks

Sasikumar.S

[AMINET]

Hi @subramanis,@sagha 

thanks for your reply, highest route is the first in the table, for example in this case I want to use port 2 as primary (this is just a lab).

[sagha]

Hi AMINET, 

Routing on FGT is not dependent on the order the routes show up in the routing table.

Factors that decide routing decisions:

1. Administrative distance.

2. Priority

3. If both are same, then interface index is looked at and helps in deciding the interface. 

This is explained as well by @subramanis. 

Thanks, 

Shahan

[AMINET]

Hi @sagha,

But as you see in screenshot 3 it uses port 6 as primary, and I'm looking for how to make it use port 2.

thaks..

[AMINET]

Hi @sagha @subramanis,

What do you mean by "interface index"? If the index is the same as the interface number, my fortigate is using port 6 even if port 2 is the lowest number.

thanks.. 

[sagha]

Hi AMINET, 

It would be helpful to know how you would like to control it? Are you planning on controling certain traffic? 

In the article, its mentioned that:

1. If you have lower AD, that route would be preferred. 

2. If you have lower priority, that route would be preferred. 

If both are same, the interface with lowest index would be preferred. 

This can be controlled and you can use sdwan rules for this. 

Thanks, 

Shahan Agha