Windows "Your DNS Server Might Be Unavailable"

What’s actually happening

Pages won't load in the browser but ping 8.8.8.8 by IP works, which points at name resolution rather than the link itself. The Windows troubleshooter lands on "Your DNS server might be unavailable" and either can't fix it or fixes it until the next reboot. nslookup google.com times out or returns "DNS request timed out."

Common causes

• DHCP handed out a DNS server IP that's down, wrong, or unreachable from this network
• The router is advertising itself as the resolver but its own upstream DNS is dead
• Stale or poisoned entries in the local DNS client cache
• Firewall, VPN, or antivirus is blocking outbound UDP/TCP port 53
• DNS Client service (Dnscache) is stopped or stuck

How to fix it

1. Flush the resolver cacheOpen an elevated Command Prompt and run ipconfig /flushdns. Then ipconfig /registerdns. This clears stale records that survive a reconnect and is the fastest thing to try first.
2. Point at a public resolver manuallyNetwork & Internet > adapter > Edit DNS server assignment > Manual. Set IPv4 preferred 8.8.8.8, alternate 1.1.1.1. If resolution works immediately, the DHCP-assigned server was the problem — fix it at the router or leave the static entry.
3. Restart the DNS Client serviceservices.msc > DNS Client (Dnscache) > Restart. If it's disabled, set it to Automatic. A wedged Dnscache produces the exact "unavailable" verdict even when the upstream server is healthy.
4. Reset the TCP/IP and Winsock stackIn an elevated prompt: netsh winsock reset and netsh int ip reset, then reboot. This clears corrupted socket/LSP state that intercepts or drops port 53 traffic.
5. Check what's blocking port 53Temporarily disable third-party AV/firewall or disconnect the VPN and retry nslookup. Security suites with "network protection" and some VPN kill-switches silently swallow DNS — whitelist or reconfigure rather than leaving protection off.