DNS_STATUS_FQDN (0X00002555) – DNS name is a fully qualified DNS name

When Does This Error Pop Up?

You're trying to connect to a server or a device on your network – maybe a file share, a printer, or a remote desktop. The connection fails, and you see something like DNS_STATUS_FQDN (0X00002555) in the event log or a tool like nslookup. I've seen this exact error last month with a client's accounting software that tried to resolve server01.company.local. (notice the trailing dot) instead of server01.company.local.

Root Cause – The Trailing Dot Problem

The error code 0X00002555 translates to “DNS name is a fully qualified DNS name.” That sounds fancy, but it's simple: the DNS name you're using already has a dot at the end. In DNS, a trailing dot means “this is the complete name.” Normally, Windows DNS appends your domain suffix to incomplete names. But if the name already has that dot, Windows gets confused – it thinks the name is already fully qualified and won't try to add a suffix. So the resolution fails if the name isn't exactly correct.

Common triggers:

• An application hardcodes a name with a trailing dot (like mail.server.com.)
• DNS suffix list on your network adapter is wrong or missing
• A group policy pushes a bad DNS suffix
• Someone manually typed a dot at the end in a config file

The Fix – Step by Step

1. Check the exact name causing the issue.
   Look at the app or tool that triggered the error. In Event Viewer, filter for source DNS Client Events and look for event ID 1014 or 1016. The error message will show the name. If it ends with a dot, that's your culprit.
2. Remove the trailing dot from the application config.
   If it's a hardcoded name, edit the config file or app settings. For example, in a printer's web interface or a database connection string. Remove the trailing dot.
3. Fix the DNS suffix on your network adapter.
   Open Network Connections, right-click your active adapter, choose Properties, then select Internet Protocol Version 4 (TCP/IPv4) and click Properties. Click Advanced, go to the DNS tab. Under DNS suffix for this connection, make sure it's correct – like company.local or office.domain.com. Uncheck “Append parent suffixes of the primary DNS suffix” if you don't need it. Then check “Append these DNS suffixes (in order)” and add your domain.
4. Delete any bad registry entry for DNS suffix.
   Open Regedit (run as admin). Go to HKLM\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{your adapter GUID}. Look for Domain or DhcpDomain values. If they have a trailing dot, remove it. Backup the key first.
5. Flush DNS cache and test.
   In Command Prompt (admin), run:
   ipconfig /flushdns
   Then try the failing operation again.

What If It Still Fails?

Sometimes the fix isn't on your machine – it's the DNS server itself. If you're using a local DNS server (like Windows Server or a router), check if the server has a misconfigured forward lookup zone. For example, your zone might have a root zone (a dot at the top) that shouldn't be there. In DNS Manager, look for a zone named just “.” – that's a root hint zone, not a problem normally. But if someone created an empty root zone accidentally, delete it.

Also verify the application isn't using a hardcoded IP or a host file entry. Check C:\Windows\System32\drivers\etc\hosts – stray entries with trailing dots cause the same issue.

Had a client once where a custom VPN app was adding a dot to the DNS suffix every time it connected. The fix was to update the app's config file and stop the service from overwriting the DNS settings.

Quick Check: PowerShell Command

Run this to see your current DNS suffixes and check for trailing dots:

If any suffix shows a dot at the end, you've found the problem.

Final Word

The 0X00002555 error is annoyingly specific but easy to fix once you know the root. It's almost always a trailing dot or a missing suffix. Don't waste time rebuilding DNS or reinstalling apps – check the name first. That's where 90% of the fixes live.