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HT_JDC
HT_JDC
New Member
March 19, 2025
Question

Automatic taking out WAN if the speed is decreased at SD-WAN aggregation.

  • March 19, 2025
  • 1 reply
  • 534 views

Hello Experts,

 

Let us assume there is a SD-WAN aggregation with WAN-A and WAN-B.
Can we have a configuration so that only WAN-A is used

when WAN-B bandwidth is less than a specific speed (eg. < 1Mbps)

and WAN-B is automatically taking out from the aggregation?

 

Best regards,

 

 

1 reply

Christian_89
Christian_89
Contributor III
March 19, 2025

Out of the box, FortiOS SD-WAN does not support a direct configuration that automatically removes a WAN interface solely based on its bandwidth falling below a specific threshold (e.g., <1 Mbps).

Instead, SD-WAN relies on performance SLA monitors—typically using metrics such as latency, jitter, and packet loss—to evaluate each link’s health. If a link fails to meet the defined performance criteria, the SD-WAN rules will steer traffic away from it in favor of a better-performing path.

If you specifically need to take WAN-B out of the aggregation based on a bandwidth threshold, you have two options:

- **Indirectly via Performance SLAs:**
Adjust your performance SLA thresholds so that when WAN-B’s overall performance degrades (which might indirectly reflect a lower effective bandwidth), it no longer meets the criteria, and SD-WAN will stop routing traffic through it.

- **Custom Automation/Scripting:**
Implement external monitoring (e.g., via FortiManager’s API or another monitoring solution) that checks the link’s available bandwidth. Based on that, you could dynamically adjust the SD-WAN configuration to remove or re-prioritize WAN-B.

In summary, while there isn’t a built-in setting to remove a WAN interface strictly based on bandwidth metrics, you can use performance SLAs or external automation to achieve a similar outcome.

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