multi Required SLA Target or multi probing detect server?

Question

greetings all,I created two SLAs, they have the same settings (same interface participants, same SLA target, same link status metrics) but only with different detect server (probing target). SLA 1 probing 10.74.a,b, SLA 2 probing 172.29.x.y. And, I added the two SLA under the same SD-WAN rule, which is with lowest cost (SLA)the question is , what is the Boolean logic here? Let's say, 15 consecutive times of probing failure occurs to either one of the two (1 out of 2) SLAs , will the related interface become inactive? and will the SD-WAN switch to the secondary interface (the interface with higher cost)?AND, what about if I add the two probing detect servers to the same SLA? and only use the one SLA under the SD-WAN rule?Thanks,Sean

sean3 · Accepted Answer

great explanation, thanks a lot, we are almost there. Can you please review my thought here?

In practice, it seems both way :

multi probing detect server configured under the same performance SLA, and use the single SLA under sd-wan rule;
or single probing detect server for each performance SLA but both SLA being used under sd-wan rule

can bring the same operational result.

In way 1, both SLA servers must fail to consider the SD-WAN member as dead. If either of them is reachable, the member is considered alive. So, in this scenario, the SD-WAN rule will not switch to the other interface if only one of the SLA server is unreachable.

In way 2, just like you mentioned, it also works in the same way as way one.

In my production, I used the way 2, because I also need visibility of each SLA performance in fortigate and FortiAnalyzer for both detect server, if I add the two server under a single SLA, then I don't have a good visibility for each of the server (as being illustrated Technical Tip: SD-WAN Performance SLA with Multiple Servers ). And I don't want the sd-wan trigger the failover if only 1 SLA fails, instead I want the failover to occur when both SLA fail (for 15 consecutive times, in my case).

Dhruvin_patel · Answer

Greetings!

If you have two separate Performance SLA Rules, both rules must fail simultaneously for the related interface to become inactive. Therefore, if only one of the two SLAs fails (e.g., 15 consecutive probing failures), the interface will not be marked as inactive, and the SD-WAN will not switch to the secondary interface.

When you configure multiple probing servers within a single SLA, it operates as an 'AND' circuit. This means that both probing servers must fail for the SLA to trigger a failure state. If only one server fails, the interface will remain active.

I hope I answered your query.

Regards!

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