Access via DNS name works, direct IP access does not

[dayzd]

As you might have picked up from the title, I've got myself a weird problem.

 

All of my servers do a manual, weekly backup to an SMB share on a remote NAS box. All of the servers work fine with this, except one, which I've found is down to the confusing problem outlined above: when accessing the NAS device by it's DNS name, everything is fine, but if I access it via IP address (which the backup process is set to do), every connection attempt fails leading the backup to error out claiming 'The specified network name is no longer available'.

 

The easiest thing to do here would be to change the script that runs the weekly remote backups to use the DNS name, but I don't want to have to rely on working DNS for any potential disaster recovery plan.

 

Has anyone come across anything like this before? I've Googled a bit, but have so far found nothing that has helped, so I'm open to suggestions!

[dayzd]

Further details:

• pinging both the IP address and the DNS name of the NAS from the troubled server both work correctly.
  
• pinging both the IP address and the DNS name of the troubled server from the NAS both work correctly (via DNS the time between pings is slow while the actual response time stays the same).
  
• pinging both the IP address and the DNS name of ANOTHER server from the NAS both work correctly (via DNS the time between pings is slow while the actual response time stays the same).
  
• Other servers (both build from the same initial image, and different machines completely) can all access the NAS via DNS name and IP address with no problems.
  
• Accessing other SMB shares from the troubled server via both DNS and IP address works correctly.
  

[dayzd]

Further testing and general fiddling about has shown my original conclusion is now wrong - it's not a DNS vs direct IP connection problem, it's just a flat-out connection problem.

 

Whichever way I connect to the NAS from this server now, it loads the list shares available, but then times out when I try to connect to any of them.

[simonm]

You haven't got a duplicate IP address have you ?.. that can cause intermittent connection issues ( to say the least)

[dayzd]

Nope, not a duplicate IP. Important stuff is static and I keep a good track of what is in use.

 

Taking a closer look at the NIC settings on the troubled server, I've changed the Jumbo Frames value, which looks like it has fixed the share access - I can browse the NAS' shares by IP or DNS name properly now.

 

Going to have to wait until after the weekend to see if it has resolved the backup issue. Fingers crossed!