Check DNS before blaming the network
Many "the network is slow" tickets come down to slow or failing DNS lookups. Here's a practical order for ruling DNS out in minutes.
Sample article to show the layout. Replace it with your own writing.
When a "the network is slow" ticket comes in, attention usually goes to links and switches. But a large share of these tickets turn out to be DNS latency, not the network itself.
Why slow DNS looks like a slow network
Almost every connection starts with a DNS lookup. If the answer takes two seconds, the page feels slow to the user even when the link is perfectly fast.
The order to check
- Measure lookup time from the user's own machine, not the server.
- Compare the internal resolver with a well-known public one.
- Check the resolver order on the client; the first one may be down.
- Review resolver logs for SERVFAIL errors or timeouts.
Useful commands
dig example.com +stats
dig @1.1.1.1 example.com +stats
resolvectl statusLook at the Query time line. A large gap between the internal and public resolver usually points to the internal resolver or its forwarding configuration.
The takeaway
Ruling out DNS takes minutes, and it can save hours spent testing healthy links.