SDwan SLA behavior

1 reply
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Here's a scenario,

I have a branch fortigate using a base configuration which uses two ISPs for the virtual link. In this case we do not yet have the link for WAN2 (Waiting on the carrier to install)

So in the SDwan we see WAN1 up and WAN2 down.

When hitting an SLA on wan1, does the fortigate bring wan1 down until it it meets SLA? Even if WAN2 is hard down? Or is there some sort of safety built into this since WAN2 is hard

FortiGate

kchengAnswer

Staff & Editor

Hi,

Based on your description, the failover will not happen as WAN2 is having the worst possible SLA (down entirely). When you configure SDWAN rules, the selection of the outgoing interface depends on the strategy that you deployed. The SDWAN rules compare the SLA between all the member interface configured on the rule. Hence, in your case, WAN1 will still be chosen as the outgoing interface as FortiGate determine that WAN1 has a better SLA performance compared to WAN2 despite it violates the SLA measurement that you set.

kchengAnswer

Staff & Editor

Hi,

Based on your description, the failover will not happen as WAN2 is having the worst possible SLA (down entirely). When you configure SDWAN rules, the selection of the outgoing interface depends on the strategy that you deployed. The SDWAN rules compare the SLA between all the member interface configured on the rule. Hence, in your case, WAN1 will still be chosen as the outgoing interface as FortiGate determine that WAN1 has a better SLA performance compared to WAN2 despite it violates the SLA measurement that you set.

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