Technical Tip: DNS latency calculation change

Description

This article describes changes to latency calculation.

Scope

FortiGate v7.4.4 and v7.6.x.

Solution

In the other versions, FortiGate will downgrade the server by increasing the Latency value by about 13-15 Seconds when a failure count occurs to choose the next available server to send the DNS request.

Instead of increasing the time to 15 seconds, It will incorporate the following:

• Server failure counts as a latency penalty at server selection time.

• FortiGate will Only adjust the RTT when a response has been received.

To check the DNS server latency value:

diagnose test application dnsproxy 2

DNS latency info:
vfid=0 server=4.2.2.2 latency=10 updated=5343
vfid=0 server=8.8.8.8 latency=1 updated=53

Related articles:

• Technical Tip: DNS show High Latency Value 15000 ms 

• Technical Tip: Clarifying differences between 'diagnose test application dnsproxy 2' information in the CLI and the GUI