When Windows tells you the DNS server is unavailable, the DNS server is usually fine. The message is what the network troubleshooter prints whenever name resolution fails, and the actual cause is far more often your resolver setting, a stale cache, or the router than an outage at Google or your ISP. The fastest way to fix it is to work the causes in order of cost - the free thirty-second checks first - instead of rebooting everything and hoping.
This is a diagnosis-order problem, not a single-fix problem. Here is the order that finds it fastest, from the cheapest cause to the most involved.
Table of contents
- First: is it DNS at all?
- Cheap fixes, in order
- The resolver setting is the usual culprit
- When it is the actual server
- How this fits the rest of the stack
- FAQ
First: is it DNS at all?
Confirm the failure is name resolution and not the whole connection. Ping an IP directly, then a name:
ping 1.1.1.1 # if this works, your connection is up
ping cloudflare.com # if THIS fails but the above worked, it is DNSIf the IP responds but the name does not, you have confirmed it is a DNS problem specifically - which is the single most useful thing to know, because it rules out half the possible causes immediately. If neither works, the problem is the connection, not DNS.
Cheap fixes, in order
- Flush the local cache. Windows:
ipconfig /flushdns. macOS:sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder. Clears a stale entry in seconds. - Change your resolver. Set DNS to
1.1.1.1or8.8.8.8. If that fixes it, your ISP’s resolver was the problem, not your machine. - Restart the router. A caching resolver on the router can wedge. Power-cycle it and wait a full minute for it to come back.
- Renew your IP lease. Windows:
ipconfig /releasethenipconfig /renew. Clears a bad DHCP-assigned DNS server.
Ninety percent of ‘DNS server unavailable’ errors are gone by step two. Doing these in order means you find the cause instead of changing five things at once and never learning which one mattered.
The resolver setting is the usual culprit
The most common real cause is a bad or unreachable DNS server configured on the adapter - sometimes left behind by a VPN that did not clean up, sometimes an ISP resolver having a bad day.
# Windows: see what DNS server you are actually using
ipconfig /all | findstr "DNS Servers"
# macOS / Linux:
scutil --dns | grep nameserver # macOS
cat /etc/resolv.conf # LinuxIf the listed server is something you do not recognize, or a 10.x/192.168.x address that no longer exists, that is your problem. Set a known-good public resolver explicitly and the error clears. A VPN client that crashed is a frequent source of a leftover, unreachable DNS entry.
When it is the actual server
Occasionally it really is upstream. Public resolvers have outages, and if you run your own authoritative DNS, it can go down. To tell the difference, query a different resolver directly:
nslookup example.com 1.1.1.1
nslookup example.com 8.8.8.8If both public resolvers answer but your configured one does not, the configured server is down - switch resolvers and move on. If you run the authoritative server for a domain and nobody can resolve it, that is a real outage on your side, and the logs on the server are where you start rather than your laptop.
How this fits the rest of the stack
A cheapest-cause-first order is what turns ‘DNS server unavailable’ from an afternoon into two minutes, and it is the same discipline that keeps production incidents short: check the free things before the expensive ones. When you run services, you want the resolution path and the logs in one place so ‘is it DNS’ is answerable in seconds. The RunxBuild hosting calculator shows a service and its bandwidth as line items, and the RunxBuild dashboard is where the deploy and DNS status live together.
Useful related references:
- How to fix DNS server not responding
- DNS address could not be found
- ipconfig /flushdns explained
- Static sites and domains on RunxBuild
FAQ
Why does it say my DNS server is unavailable?
Windows prints that message whenever name resolution fails, regardless of the real cause. Most often the problem is a bad or unreachable resolver configured on your adapter, a stale local cache, or the router, not an outage at the DNS provider. Confirm it is DNS by pinging an IP and a name, then work the cheap fixes: flush the cache, switch to a public resolver, restart the router.
How do I fix DNS server unavailable on Windows?
Run ipconfig /flushdns to clear the cache, then set your DNS to a public resolver like 1.1.1.1 or 8.8.8.8. If that does not help, run ipconfig /release and ipconfig /renew to get a fresh DHCP lease, and restart the router. Check ipconfig /all to see which DNS server you are actually using; an unrecognized or dead address is the usual culprit.
How do I know if the problem is DNS or my connection?
Ping a raw IP such as 1.1.1.1 and then ping a domain name. If the IP responds but the name does not, it is specifically a DNS problem. If neither responds, your connection itself is down and DNS is not the issue. This one test rules out half the possible causes in a few seconds.
Can a VPN cause DNS server unavailable errors?
Yes. A VPN client that disconnects or crashes can leave behind a DNS server entry pointing at an address that is no longer reachable. Check the DNS servers on your adapter; if you see an unfamiliar or private address that no longer exists, remove it and set a known-good public resolver. This is one of the most common real causes.
How do I check if a DNS server is actually down?
Query a known-good public resolver directly: nslookup example.com 1.1.1.1 and nslookup example.com 8.8.8.8. If the public resolvers answer but your configured server does not, your configured server is the one that is down, so switch resolvers. If you run the authoritative DNS for a domain and no resolver can answer, that is a real outage on your side.