Accessing Synology NAS via numeric IP works fine, but asks for credentials via name

I used to be able to access my Synology NAS by name (e.g. \\synology), but now, when I try that, regardless of user or pc, it prompts me for a username/password in Windows. However, if I put in the numeric IP for the NAS (\\, I can access it fine. Any idea what could be causing this issue?

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Dan LuteyCommented:
Check the synology and see if the network settings is pointing to the correct DNS server. If it is then check your DNS and see if the synology is listed. If not you can add it. Then you should be able to map it by host name.
A quick test - can you ping the Synology NAS by name?  If you get a reply then the DNS is not the problem.  If not then follow Dan's suggestion to check the DNS configuration on your NAS.  Additionally, check to make sure that both the Synology and the workstation you're trying to access it from are pointing to a common internal DNS server.
I've also experienced your scenario when accessing shared folders on my network and even an older Buffalo NAS. For me using the name \\SHARENAME to get to the shared folder used to work, then suddenly I can only do it via \\

Did you log in with credentials to the NAS or mapped a network drive to it? If yes, does this only happen from one computer? If yes, perhaps you can go to Manage Windows Credentials and delete the login credentials for that connection or share.
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Carlos IjalbaIT Systems DirectorCommented:
You obviously have an incorrect DNS resolution, to see what's the problem you'll have to perform DNS problem resolution, using the commands:

ping synology
ping -a
nslookup synology

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And see if they match, if they do not, there is your problem.

You can also fix it temporarily by adding the name resolution directly on your PC:

Edit C:\Windows\System32\drivers\etc and add:    synology

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ruhkusAuthor Commented:
Thanks everyone for the feedback.

Dan - the DNS server it's pointing to has both the forward and reverse lookup zones correct for the Synology NAS.

Wayne88 - I can ping it by name and it responds fine on my PC. Both my PC and the Synology point to the same DNS server (I have multiple DNS servers, but on the Synology I could only add one, although this is the first one listed on my PC as well, FWIW)

mwyatt - I used to have it mapped with the Synology name and that stopped working. When I remapped it with the IP address it works fine. I did confirm previously that I did not have any credentials stored in the Credential Manager.

Carlos - ping and nslookup both resolve fine on my PC. The issue isn't just on my PC though, but all other machines I've tested.

Some more info - the Synology is joined to my domain, but none of my domain credentials work when I do try to log in (when doing \\synology). However, I can log in if I use my Synology local account.
As noted though, I can get in fine with the numeric IP without any credential prompt.
Does the Synology normally require credentials to access it?
ruhkusAuthor Commented:
Yes it requires credentials. I've joined the Synology to the domain and active directory. I've assigned AD permissions to the folders I want to share on the Synology. It seems these AD credentials are passed along fine when an AD user accesses the Synology via numeric IP.

When I try with the name, I get the "Logon failure: unknown name or bad password" error on an "Error Network Password" screen. Re-typing my AD credentials does not work as well, only the local Synology account I created will work here.
So you did input credentials at one time, probably when you mapped a drive letter to it.

I realize you say the credentials aren't stored, but if it isn't asking for credentials with an IP address then logically they are still stored somewhere on your computer, right? When I look in my Windows Vault I see several credentials headings: Windows Credentials, Certificate-Based, and Generic Credentials. Mappings to one of my servers shows in TWO places in my vault - Windows and Generic. I've had this solve the problem more than once, but not every time.

I've also had success by re-mapping a drive letter and choosing "Connect using different credentials". Does this help? FWIW, I'm mapping to a Win2008 server but we don't use AD.

Sadly, for those time where deleting credentials and re-mapping didn't work, I've added entries to the HOSTS file on the affected PCs. Not elegant but I just got tired of dealing/troubleshooting. I could never resolve by flushing, resetting, etc. and had to wait until reimaging the computer or replacing it.

Can you access it by FQDN?
Carlos IjalbaIT Systems DirectorCommented:
You can try deleting the synology account from the domain, and adding it again, following Synology's step-by-step HowTo:
Carlos IjalbaIT Systems DirectorCommented:
Hello ruhkus

Any luck???
Jackie ManCommented:
Restart the Synology NAS.
ruhkusAuthor Commented:
I finally figured this out. The answer was in the link that Carlos provided, in section 2.1 -

"Please use the same time server on the entire Active Directory Network. The Synology NAS, all Domain Clients, and Active Directory server should all be using the same NTP server to have their time exactly synchronized. Most common Domain errors (e.g., accessing shares via DNS name, access permission errors) can be resolved by having a properly synchronized time server. The time server can be an NTP server outside the network, or the NTP service of the Active Directory Domain Controller."

I changed the time sync from an external server to my DC and that resolved the issue. I guess at the beginning, the time was in sync, but then differed by too much so it stopped working.

Thanks everyone for your help.

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Carlos IjalbaIT Systems DirectorCommented:
Good to hear that you got it sorted, ruhkus.

Note that time differences can affect a lot of devices connections when there is a time difference greater than 5 minutes: Stock exchange notifications, kerberos authentication, LDAP sync, HA heartbeats in clusters, DNS syncs, etc.

So it is always a good idea to have a good NTP server, hopefully dedicated and with connections to at least 2 different countries NTP server pools, or use your network cores as NTP servers (usually the DCs or DNS servers).
ruhkusAuthor Commented:
The other solutions helped me troubleshoot, but ultimately I found the actual issue by reading one of the links posted for a different possible solution.
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