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Best choice for link quality

Hey guys.

I wanted to understand how to better treat the SLA and the health check.

My doubts:

1 - When I select custom SLA, the percentage specified in "maximum lost packet" is based on the "Example size for SLA" right?

2 - If I have packet loss reaching the metric defined in my SLA. It deactivates the link regardless of the "health check" action of "deactivate the gateway after" x consecutive times, right?

3 - The values in "maximum lost packet" in SLA and "deactivate gateway after" do you need to be careful? Any ideal value?
Example: if there is a value of 10% loss of an example of 30 and action of deactivating the gateway after 1 consecutive failure. The link presents oscillations, varying some packet losses, so the action will be to deactivate and return after 3 successes. If we are using this link will we notice the flaws and it will never be replaced?

4 - SLA sees the amount of packet lost in general. Whether it is a consecutive loss or not, it is within the loss metric it changes. Right?

5 - Are the graphs always created based on the example or is it for each packet triggered?

Thank you for the patience.

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0 Raphael Alganes 11 months ago

Hello Gib GoDesk ,

Thanks for reaching out to Sophos Community.

There are recommended SLA values for a specific SD-WAN Profile that you can follow:

Additionally, you may refer to this SD-WAN doc guide for more details: https://doc.sophos.com/nsg/sophos-firewall/20.0/help/en-us/webhelp/onlinehelp/AdministratorHelp/Routing/SDWANRoutes/SDWANProfiles/index.html#failback-to-the-original-gateway

For #5 - Do you mean under Diagnostics > SD-WAN Performance? Could you elaborate more what are you searching for the feature exactly?

Regards,

Raphael Alganes
Community Support Engineer | Sophos Technical Support
Sophos Support Videos | Product Documentation | @SophosSupport | Sign up for SMS Alerts
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0 Gib GoDesk 11 months ago in reply to Raphael Alganes

I have the feeling that the link strategy is not good. I feel that there are internet slowdowns because the main link is oscillating between rising and falling continuously due to the SLA and health check choices.

I have already read the documentation and some others.

Sophos' recommendation is only for SLA, but it does not explain the best way to do it with a health check.

I have defined the SLA:

Maximum latency: 150ms
Maximum jitter: 30ms
Maximum packet loss: 5

At the health check:

Protocol: Ping
Probe target: 1.1.1.1

Health check attempts
Interval between checks: 2
Response time-out: 2

Deactivate gateway after: 2
Activate gateway after: 10
Sample size for SLA: 30

Link A was oscillating and instead of staying on Link B, we felt the operator's small faults. Image below:

Loss below the SLA line does not cause the switch, but it seems to me that deactivating the gateway caused the link to be disconnected.

Regarding the graph, I'm not sure if it is generated by each test probe sent only or if it generates every 30 completed samples.
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