How do you fix a DNS server problem?

March 04, 2026 · 8 min read

Quick Answer

To fix a DNS server problem, restart the connection, flush or reset DNS settings, switch to a known public resolver, and verify that the domain resolves correctly from your device.

DNS issues are often treated as a single problem, but the failure point can be local cache, router settings, ISP resolvers, or blocked traffic. The fastest fix is to narrow down where resolution stops working.

Step-by-step solutions

Confirm whether the whole network is affected or only one device.
Restart Wi-Fi, Ethernet, or the router to clear transient state.
Flush local DNS cache and retry the lookup.
Change the resolver to Cloudflare, Google, or Quad9.
Test another domain and compare results.
Check whether VPN, parental controls, or security software are intercepting DNS.

Useful commands

Windows

ipconfig /flushdns
ipconfig /renew
nslookup dnsbenchmark.app

macOS

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder
scutil --dns

Linux

sudo systemd-resolve --flush-caches
resolvectl status
getent hosts dnsbenchmark.app

When to go deeper

If the resolver settings themselves are damaged, follow how to reset a DNS server. If the issue looks like stale results rather than total failure, go next to how to clear DNS cache. If a security product or network policy may be interfering, check whether DNS is blocked.

FAQ

What causes DNS server problems?

Common causes include bad resolver settings, ISP outages, stale cache entries, router issues, blocked DNS traffic, or resolver timeouts.

Will restarting the router fix DNS?

It often helps because it refreshes network state, renews settings, and can clear temporary resolver issues.

Should I use public DNS to troubleshoot?

Yes. Switching temporarily to Cloudflare, Google, or Quad9 is a good test to determine whether the ISP DNS is the problem.

Why does DNS fail on one device only?

Per-device cache corruption, VPN settings, browser secure DNS, or manually configured resolvers can create device-specific DNS failures.

Test your DNS now

Download DNS Benchmark for free and find the fastest server for your network.