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

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 \\192.168.1.60.

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.

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 192.168.1.10
nslookup 192.168.1.10
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:

192.168.1.10    synology

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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?

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?

Hello ruhkus

Any luck???

Restart the Synology NAS.

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).

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.