I have a Windows Server 2012 R2 AD Domain.

All clients are running fully updated Windows 10 Pro.

I have some servers (Synology), fully updated.

Up until now, I can access all Synology servers just fine from Windows Explorer using \\SynServerName.

Now, I have ONE server, running Windows Server 2012 R2, that can't access ONE Synology server using \\SynServerName. It DOES work if I use \\SynServerName.domain.com.

From the same 2012 R2 server, ping SynServerName works and responds from the correct IP. nslookup SynServerName shows the correct IP and furthermore the DNS result is listed as SynServerName.domain.com.

I can access OTHER Synology servers from the same 2012 R2 server using Windows Explorer just fine. One or two weeks ago, I could access all Synology servers just fine.

Using OTHER Windows 2012 R2 servers on the same network, I can access all the Synology servers just fine. Using OTHER Windows 10 Pro clients on the same network, I can access all the Synology servers just fine.

It is just this ONE Windows 2012 R2 server, that can't access ONE Synology server using the host name from within Windows Explorer.

All the clients, all the servers, and all the Synology servers relevant to this problem, are on the same physical network, the same subnet, and joined to the same domain and using the same DNS.

This is a terribly unimportant issue, but little things like this bug me. Any ideas?

  • It’s probably somehow related to the difference between DNS and NetBIOS name resolution. – Daniel B Jul 10 '18 at 8:17
  • and NETBIOS name resolution from Command Prompt would follow different steps vs. resolution via Windows Explorer? – Daniel Jul 10 '18 at 8:41
  • Compare the output of ipconfig /all between a working and the non-working server. Do you see any differences in their configurations? – Twisty Impersonator Jul 10 '18 at 11:42
  • Aside from the expected stuff like host name, MAC ID, and static IP, they are identical. Furthermore, this problematic server has had no problem accessing the same Synology server for months, and no changes have been made to the network config recently. Only automatic Windows updates... – Daniel Jul 10 '18 at 13:15

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