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I'm not really sure if this is a Synology issue or a Windows issue.

I'm running all Windows 10 Pro machines on a Windows Server 2012 R2 domain. With somewhat disturbing frequency (let's say 5% of the time), UNC paths to my Synology boxes don't work (as in, trying to browse to \\synology-server\ in Windows Explorer), and I must browse using the direct IP address of the box (like \\192.168.1.10\).

This affects some of my GPOs as I deploy some shared network folders as shortcuts to my users using UNC paths to the Synology boxes. After bringing this up to Synology support, they recommended I always use the IPs for reliability, but I really don't see why UNC paths shouldn't be just as reliable.

FYI, I am running DNS servers from two local Windows Server 2012 R2 boxes (both of which are also DCs), and both those DNS servers are assigned to my client machines via DHCP. Even stranger, when the UNC path is not working in Windows Explorer, I can ping the server name and nslookup the server name with instant responses from my DNS servers.

Any ideas on what I can do to troubleshoot this situation?

Ryan Babchishin
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Daniel
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  • Search for Strict Name Checking; https://support.microsoft.com/en-sg/help/3181029/smb-file-server-share-access-is-unsuccessful-through-dns-cname-alias – Stephan Aug 29 '19 at 11:43

3 Answers3

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I was having the same problem and it took me a couple of hours to figure out, so thought I'd share it.

Go to your Synology's Control Panel -> Network -> Advanced Settings (under General Tab) : Uncheck 'Reply to ARP Request if the Target IP address...'

Once you hit apply it may take a couple of minutes to reflect and BAAM. Works like a charm!

Hope this helps

Tamer
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It does sound like you should be focusing on DNS. A path with a host name like \\servername\ requires DNS or WINS or NetBIOS name resolution, all/any of which should be provided by your domain controller. Can you set a static entry for your Synology server in DNS and then verify that it can be properly resolved (nslookup) before trying to access the share? Perhaps that will help. Just guessing here.

Ryan Babchishin
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  • the Synology server is joined to the domain, so it automatically has a DNS entry in the DC. I have performed `nslookup` while my UNC browse fails, and I get instant response from the DC/DNS Server with the correct IP. It makes no sense. Similarly, I can `ping` the UNC name and it responds from the correct IP. – Daniel Aug 23 '16 at 00:46
  • @Daniel Yes it does make no sense – Ryan Babchishin Aug 23 '16 at 05:48
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If the above solution from @Tamer doesn't work AND you are not running a DC, try the following:

Go to your Synology's Control Panel -> Network -> DSM Settings -> Uncheck "Enable Customized domain".

Removing the check mark fixed the issue immediately for me on my DS1815+. I'm using a Ubiquiti USG as my DHCP server, DNS server, and gateway.

Chris
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  • Is your Synology connected to a domain? I assume not since you said "not running a DC" - just wanted to make sure – Daniel Mar 25 '19 at 15:20