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SBS 2008 To Windows Server 2012 R2 Question

Hello. I am in the process of migrating from SBS 2008 to Windows Server 2012 R2. I have transferred all 5 FSMO roles to the the new server and removed the SBS 2008 server as a Global Catalog server. In addition, DHCP has been moved to the Windows 2012 R2 server. Everything seems to be running okay. Before I DCPROMO the SBS 2008 server and remove it from the network, I wanted to test things so I disconnected the network cable from the SBS 2008 server. This seems to have had an impact on internet communications as browsing to web pages seems to take a long time with messages of "Resolving host". Eventually everything loads, but it is nowhere near as fast as when I reconnect the SBS 2008 server. The DHCP server is pointing to the new server for DNS and the new server has itself listed as the DNS server. Ipconfig on clients point to the new server as well for DNS.

Is this issue because I have not DCPROMO'd the old server? Or could there be somewhere else that I need to check?

Thank you.
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ctsuhako
Asked:
ctsuhako
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1 Solution
 
Leon KammerCommented:
Often a DNS Forwarder record gets left behind when migrating to a new DNS server.
In his case, the DNS server is very slow with external DNS lookups because it forwards requests to a DNS server that no longer exists, the DNS service will follow a time-out algorithm when it sends the query to the first Forwarder in the list.
If there is no response after the TTL, then it eliminate that Forwarder for this query only, and it will then send the query to the next Forwarder in the list. If none of the Forwarders respond the process eventually fails and finds and alternate DNS path for resolution.

Look for and remove the obsolete DNS forwarder records from the DNS server.
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ctsuhakoAuthor Commented:
Hi, Leon:

I checked the old server for any DNS forwarder records and there were none. On the new server I have forwarders listed to our ISP's DNS servers. Is there anywhere else I should look?

Thank you.

Clay
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RizzleCommented:
Are your clients getting the correct dns server via dhcp? If you statically assign the dns server to a client with the issue does the issue still occur? How long has this issue been going on for?
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Leon KammerCommented:
Hi Clay,

Have you made sure DNS on PC's are pointing to the correct server?
If the lease time has not expired, it will be looking for the old server.

Use ipconfig /all|more and check the DNS Servers are correct.
Or you could use  ipconfig /renew to ensure that the client PCs have the correct DNS Server information.

Cheers

Leon
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ctsuhakoAuthor Commented:
Hi, Roshan:

Clients are getting the correct DNS server via DHCP. Statically assigning them does not a difference. Issue only happens when I disconnect the old server; otherwise everything works fine. I am leery of decomissioning the old server until I can get this resolved.

Clay
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ctsuhakoAuthor Commented:
Hi, Leon:

Ipconfig /all on clients is resolving to the correct DNS server (the new one). I am wondering if the DNS server needs time to cache resolved requests or not (I am not real versed on this).

Thank you.

Clay
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RizzleCommented:
Can you advise if you've followed the below.

https://technet.microsoft.com/en-us/library/cc755303.aspx

Also have you made your new dns server authoritative for the zone?

Maybe as a test, i would take the ip from your old dns server, shut it down and then place that ip statically on your new dns server and see if that comes back with the same issue. If it does then the issue is something to do dns not being properly migrated across.
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RizzleCommented:
Have you restarted any of your clients since doing the dns work?
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ctsuhakoAuthor Commented:
Hi, Roshan:

I will run thru the checklist tomorrow morning. I like the idea of assigning the old IP to the new server as a test. I will also try that and let you know what happens. Clients have been rebooted since change.

Thank you.

Clay
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Leon KammerCommented:
Hi Clay,

Sorry for the late response got sidetracked halfway through the post... DNS Propagation usually takes around 24 hours but usually never more than 48.
During propagation, traffic may come to either location. In essence, one client may see the new server while another sees the old one, or very rarely, all clients see the old one.

Essentially, when a Server is designated as DNS forwarder, it is responsible for handling external traffic and all of the external DNS queries in the network are resolved through it.

Cheers

Leon
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ctsuhakoAuthor Commented:
Hi, Leon:

Was out of the office for a few days. Turns out that there were no forwarders listed in the new server. Once I populated those everything seemed good! Thanks for the help.

Clay
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Leon KammerCommented:
Hi Clay,

You are very welcome.
Glad I could help.

/Leon
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