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 port5): state(dead), packet-loss(100.000%) sla_map=0x0

The following errors were observed in the link-monitor debugs:

diagnose debug application link-monitor -1
diagnose debug enable

lnkmtd::ping_do_addr_up(116): ---> port5-5-VIRTUAL_WAN_LINK-5->1.1.1.1(1.1.1.1), rcvd
lnkmtd::monitor_peer_recv(1993): ---> can not find probe for monitor port5-VIRTUAL_WAN_LINK-5, seq_num 28.

To address this, increase the probe-timeout using the CLI. This configuration is necessary when network delays are expected to exceed the probing interval (default probe timeout is 500 ms). If no probe-timeout is specified, the timeout delay defaults to the interval delay.

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     

Result.

diagnose sys sdwan health-check
Health Check
Seq(1 port5): state(alive), packet-loss(0.000%) latency(941.158), jitter(27.486) sla_map=0x0