The "DNS server not responding" error means your device reached the network but no DNS resolver returned an answer for the domain you requested. Fix it by flushing the local resolver cache, switching to a reliable public DNS (1.1.1.1 or 8.8.8.8), and confirming resolution with nslookup or dig.
Symptoms
- Browsers show "DNS_PROBE_FINISHED_NO_INTERNET" or "server IP address could not be found".
- Windows Network Diagnostics reports: DNS server is not responding.
- Ping to 8.8.8.8 works, but ping to google.com fails with "could not find host".
- Some sites load while others time out, or only cached pages open.
- nslookup returns "DNS request timed out" or "non-authoritative answer" is missing.
Common Causes
Stale or poisoned resolver cache
The local DNS cache holds an outdated or bad record. Until it expires or is flushed, every lookup for that domain returns the wrong answer or no answer at all.
Unreachable configured DNS server
The DNS server IP set on the adapter (often the router or an ISP resolver) is down, blocked, or misrouted. Queries leave the machine but never get a reply.
Router or ISP DNS outage
The router's DNS forwarder crashed, or the upstream ISP resolver is failing. This is common after firmware updates or during ISP maintenance windows.
Firewall or security suite blocking port 53
Antivirus, VPN clients, or endpoint firewalls sometimes intercept or block UDP/TCP 53. DoH (DNS-over-HTTPS) misconfiguration can produce the same symptom.
IPv6 misconfiguration
If IPv6 is enabled but no working IPv6 DNS is provided, the resolver may prefer AAAA queries that silently fail before falling back to IPv4.
Step-by-Step Fix
- Confirm the problem is really DNS, not connectivity
Open a terminal and ping 1.1.1.1. If that succeeds but ping google.com fails, DNS is the culprit. Then run nslookup google.com 1.1.1.1 to test a known-good resolver directly. A working answer proves your network path is fine and the issue lives in your configured DNS. - Power-cycle the router and clear its DNS forwarder
Unplug the router for 30 seconds, then reconnect. Most consumer routers act as a DNS proxy, and a fresh boot clears a hung forwarder process. Wait for the WAN light to stabilise before retesting from a client device. - Flush the local DNS resolver cache
On Windows, open an elevated Command Prompt and run ipconfig /flushdns. On macOS Ventura or later, run sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder in Terminal. On Linux with systemd-resolved, use sudo resolvectl flush-caches. Retest immediately after. - Switch to a reliable public DNS resolver
On Windows: Settings, Network and Internet, adapter Properties, IPv4 Properties, set 1.1.1.1 and 9.9.9.9 (or 8.8.8.8 and 8.8.4.4). On macOS: System Settings, Network, Details, DNS tab, add the same addresses. Repeat under IPv6 with 2606:4700:4700::1111 if IPv6 is active. - Reset the TCP/IP and Winsock stacks
If DNS still fails after switching resolvers, corrupted network state may be at fault. Run netsh winsock reset, netsh int ip reset, and ipconfig /registerdns from an admin prompt, then reboot. On macOS, remove and re-add the network location under System Settings. - Temporarily disable firewall, VPN, and antivirus
Pause third-party security software and disconnect any active VPN tunnel. Retest resolution. If DNS suddenly works, re-enable each component one at a time to identify which one intercepts port 53 or breaks DoH. - Verify with dig or nslookup against multiple servers
Run nslookup example.com 1.1.1.1 and nslookup example.com 8.8.8.8. Matching answers from both confirm resolution is healthy. Different or missing answers point to a filtering device between you and the resolver, which is where to investigate next. - Check for split-horizon or corporate DNS conflicts
On managed networks, an internal AD DNS server may be required to resolve internal names. Confirm the adapter is receiving the correct DHCP-assigned DNS and that a rogue static entry hasn't been left behind. Contact IT if internal zones fail to resolve.
Common DNS symptoms mapped to likely cause and first fix
| Symptom | Likely cause | First action |
|---|---|---|
| Ping to IP works, name lookup fails | Configured DNS server unreachable | Switch to 1.1.1.1 or 8.8.8.8 |
| One domain fails, others resolve | Stale or poisoned cache entry | Flush resolver cache |
| All lookups slow, then time out | Overloaded ISP or router forwarder | Bypass router DNS on the client |
| Works on mobile data, fails on Wi-Fi | Router DNS or firmware issue | Reboot router, check firmware |
| Fails only for internal hostnames | Wrong or missing internal DNS | Verify DHCP-assigned DNS server |
| Fails after installing security tool | Firewall blocking port 53 or DoH | Disable tool, test, then whitelist |
Prevention
- Set two DNS resolvers from different providers so a single outage doesn't take resolution down.
- Keep router firmware current; DNS forwarder bugs are a common fix in vendor patches.
- Document static DNS overrides so they aren't forgotten after network changes.
- Monitor resolution with a simple scheduled nslookup or a tool like DNSCheck to catch silent failures.
FAQ
Is it safe to use 1.1.1.1 or 8.8.8.8 instead of my ISP's DNS?
Yes. Cloudflare (1.1.1.1), Google (8.8.8.8), and Quad9 (9.9.9.9) are public resolvers operated at scale with strong uptime and published privacy policies. They typically resolve faster than residential ISP DNS. Review each provider's privacy statement to pick one that matches your requirements.
Why does my DNS work on my phone but not on my PC?
The phone and PC are using different resolvers or different network paths. If the phone is on mobile data, it bypasses your router entirely. If both are on Wi-Fi, the PC likely has a stale cache, a static DNS override, or a firewall rule blocking port 53. Flush the cache and compare the DNS settings on each adapter.
How do I know if the problem is my router or my ISP?
Bypass the router: on a client, set DNS manually to 1.1.1.1 and retest. If resolution now works, the router's forwarder is the issue. If it still fails, run a traceroute to the public resolver. Loss beyond your router's WAN interface points to the ISP or an upstream carrier.
Need hands-on help restoring DNS across your network? Contact RankNow IT support for a diagnostic session.