Technical Tip: How to configure performance SLA for high latency links (>500ms)

[ighita]

Description

This article describes how to configure the health check for SD-WAN links with high latency.

Scope

FortiGate.

Solution

With the default settings, the performance SLA will show a link with latency higher than 500 ms as down:

diagnose sys sdwan health-check

Health Check:

Seq(1 port1): state(dead), packet-loss(100.000%) sla_map=0x0

By default, the probe-timeout has the value of 500 ms, therefore if the link has a higher latency the probe will fail.

The solution is to increase the probe-timeout from CLI.

V6.2.

config system virtual-wan-link
config health-check
    edit <name>
        set probe-timeout 2000

V6.4, v7.0, v7.2, v7.4 and v7.6:

conf system sdwan
config health-check
    edit <name>
        set probe-timeout 2000   
        set probe-timeout   <----- Time to wait before a probe packet is considered lost (500 - 3600000 msec, default = 500).

Result.

diagnose sys sdwan health-check
Health Check
Seq(1 port1): state(alive), packet-loss(0.000%) latency(941.158), jitter(27.486) sla_map=0x0