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I rencently did an upgrade from 2003 AD to 2008 AD onto a new box. Ive kept the 2003 running as a secondary system, but i moved the FSMO files, ran everything properly including setting up the DNS.

Now heres my issue, I have random computers on my network (all static IP btw) that are flaking out for a period of 5-15 minutes. They can see external IP addresses fine (I use 4.2.2.2 as a secondary DNS) but cant see the SQL or Sharepoint server. Have to either reboot or do a dns flush in order for it to work and even then sometimes that doesnt work.

The old server 192.168.1.10 and the new server 192.168.1.5 both seem to work and I changed all the workstaions to reflect the .5 unit. Does anyone know what could be causing this?

Im a software guy by nature, developing C# apps etc, Im not a network admin by trade so its been soewhat of a leaning curve although I do have some experience.

Thanks

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When you say "flaking out" and "can't see" those servers, can you be more specific as to what the symptoms are? Can't connect? Can't ping? Can't get name resolution? –  Coding Gorilla Jan 20 '12 at 21:17
    
Users cant go to the local sharepoint site, hrrp://gssharepoint nor can i ping the sql server, 192.168.1.7 –  gabrielVa Jan 20 '12 at 21:35
    
When you can't ping the server, is that trying to ping by IP or name? If you can't ping by IP then this has nothing to do with AD or servers, this is a network failure. If it's not pinging by name, then we're back into checking the DNS servers. –  Coding Gorilla Jan 20 '12 at 21:39
    
Hmmmm Im pinging by name. Also the end user get a page cant be found error. I do know what when i flush the DNS it comes back up... would it matter having boths machines running dns? –  gabrielVa Jan 20 '12 at 21:51
    
If both are DC's, they should both be running DNS, is that not the case? –  Coding Gorilla Jan 20 '12 at 21:52
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2 Answers

It seems to me that the computers are falling back to the secondary DNS server, which wouldn't know about your SQL or SharePoint servers. Have you tried removing the 4.2.2.2 DNS server from one or two machines and seeing if they hum along without flaking out? Do all of the computers flake out at once, or randomly?

If you're running an Active Directory domain (I assume you are based on you using SQL and SharePoint) then it's best to have all of the domain computers point to the domain controllers for DNS. You can then specify alternate DNS servers from that point if you want additional redundancy.

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He stated that he "kept the 2003 running as a secondary system", so I assume that means it's still a DC (because he mentioned he transfered the FSMO roles) which should have the DNS replicated and so DNS servers should have the same information. Although that's definitely something to look at. –  Coding Gorilla Jan 20 '12 at 21:21
    
Thats correct I have the old server still running as a DC. Reason being is that Im not 100% sure if I did everything right, like I said im a software guy by nature. I could do a dcpromo and remove the old one but if i have something wrong wouldnt it mess up my 2008 AD?? –  gabrielVa Jan 20 '12 at 21:37
    
ITs a random thing. I have about 15 or so computers, only 3-4 are showing signs of the issue. IT appears to bethe same 4 or so from what I can tell. –  gabrielVa Jan 20 '12 at 21:38
    
And yes looking at both dns's they appear to have the same entries. –  gabrielVa Jan 20 '12 at 21:58
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I would ditch the secondary DNS server (or preferably set your own one up on a dc).

4.2.2.1 or any other external DNS server will have no knowledge of your internal structure. I'm guessing for some reason the clients aren't able to use the primary DNS and are falling back to the secondary - with this internet works but not your internal stuff.

If you follow my advise and just ditch the secondary, I wouldn't be surprised if you have a period where things are worse where clients cannot even get internet, but this is the time to get really troubleshooting and fix the problem for good (although I prefer the idea of setting up a secondary, then for example on your pc only, just use the primary to help troubleshoot).

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