DNS server not responding error

What the error means

DNS server not responding is a client-side error. The operating system asked the configured resolver, normally the router or the ISP's DNS, for the address behind a domain, and the resolver did not answer in time. The error usually affects more than one site at once, which is a clue that the problem is local rather than one website.

Three situations carry the same message:

• The router or the resolver is unreachable, e.g. a dropped connection or a router restart.
• The machine's DNS settings point at a server that no longer exists, such as a VPN DNS left over after the VPN disconnected.
• A firewall is blocking DNS port 53, or a proxy is intercepting DNS.

Where the error lives

The scope in the error tells you where. Diagnostic matrix:

Fix a single device

1. Flush the local cache. Windows: ipconfig /flushdns. macOS: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.
2. Check the hosts file. On Windows it is C:\Windows\System32\drivers\etc\hosts; on macOS and Linux /etc/hosts. A stale manually added line that no longer matches the real IP produces a "not responding" symptom for that one domain. Comment an entry by adding # at the front of the line and test again.
3. Check the VPN. A disconnected after the work is usually lingering in the DNS settings. Disconnect or delete the profile and test again.
4. Check whether ports are needed. A firewall rule that blocks DNS lookups breaks Site traffic but leaves the browser connecting to raw IPs; run Test-NetConnection 1.1.1.1 -Port 53 to prove the port opens.

The restart sequence

Find the exact sequence that works for a home network, then march through it.

1. Turn off the machine's Wi-Fi and re-join the network.
2. Reboot the router and wait a full minute.
3. Change the router's DNS to a stable public resolver: 1.1.1.1, 8.8.8.8, or 9.9.9.9, so the router stops relying on the ISP resolver that keeps timing out.
4. On the machine, set the same public resolver in the network adapter settings, or set it in the VPN client if the VPN owns DNS.
5. Re-test: nslookup example.com from the command prompt. A success shows the name and an IP; a failure shows the old server.

When it is the provider

If the failure persists across every device and network, your resolving DNS provider is the likely cause. Check its status page for an outage or degraded service, and test with a public resolver such as 1.1.1.1 or 8.8.8.8 to see if the domain resolves there. If one provider keeps failing, consider changing the domain's authoritative or resolver DNS to a provider with better uptime.

For a site owner, after a DNS change, the correct posture is to wait for propagation and check with a public tool such as dig @1.1.1.1 example.com or online checkers, rather than flushing and restarting your own resolver repeatedly.

Prevention

• Make sure the domain has at least two authoritative nameservers (most registrars allocate two by default) so one resolver can answer while another fails.
• Point the router to a public resolver, so you are never dependent on the router's forwarding to a provider on a single box.
• Note the exact error moment, including whether the whole network failed at the same time, which beats a log guessing later.

When to look at the domain side

If the error persists after the machine, the router, and two networks all resolve the same way, yet the domain still fails, the fault has moved to the domain's DNS. The domain may be expired, renamed or reconfigured; follow dns-propagation-and-resolution for the record steps and domain-expired-site-down for the expiry variant.