DNS needs to be flushed on Windows Server 2012

Posted on 2013-12-09
Last Modified: 2014-02-07
I have a Windows Server 2012 with Exchange 2013 on it. The server is also domain controller and DNS server and functions as DHCP server for the clients. The client workstations vary from some Windows XP, Windows Vista, Windows 7 and mainly Windows 8 PRO.

The IP settings on the server are as follows:

Subnet mask:


Mail is working fine internally, however if I want to send any mail out externally, it gets stuck in the queue. In order to release the queue I have to flush the DNS. Mail is released, but the same issue appears after some minutes. The strange thing is that I cant find any DNS related events, beside that DNS server is started.

Is there anyone who recognizes this issue? any help is greatly appreciated.

Question by:dtwild
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Author Comment

ID: 39707803
Further to the above, before I flush my DNS I cant access any websites. It looks like a DNS issue, but cant get a hold on it.
LVL 12

Expert Comment

ID: 39707819
It looks like everything is pointing internally for DNS so the mail stays within your network beecause it can't find any recipient's mail server on your network. In order to know where to send mail out to, your DNS will need to have a trusted external DNS to use to find servers outside your network.

Add the IP address/es of your ISP's DNS to the bottom of the list of DNS servers in Advanced TCP/IP settings. Also add to the list before your ISPs DNS address.
LVL 78

Expert Comment

ID: 39707820
Do you use internally the same domain name as your public one?
Do your workstations only point to the DNS on your DC?
Does your DC DNS use forwarders in the configuration or does it go out and fetch records?

For using the same domain, your internal DNS must include the external references for the website. Mail handling is impossible unless the email client and the user distinguish .......
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Author Comment

ID: 39707823
Hi guys, thanks for your response!

1. The domain name is different compared to the public one;
2. All the workstations point directly to the DC, which is managed via DHCP;
3. I configured the DNS server with several forwarders. 2 are from my ISP, and I use the Google default.

Strangely enough, when I flush DNS I can access websites on the server and mail goes out. However some later, the network connection tells me that there is an internet connection, however I am not able to browse any sites, and the mail get stuck in the queue.
LVL 12

Expert Comment

ID: 39707832
I have a very similar setup. My external domain is different to my internal domain. All my client PCs point to the one DC.

Other than my internal domain name, I have no other forward lookup zones or conditional forwarders. I only have two of my ISP's DNS addresses listed in the list of DNSs under advanced settings. That's it.

What exactly are you forwarding and how?

Author Comment

ID: 39707839
Maybe I explained wrong, sorry for that.

The forwarders that I configured are not actually configured in a DNS forwarders zone. I accessed the DNS Management console, opened the properties for the server and accessed the tab for forwarders. This is the screen where it is possible to configure forwarders which are used to resolve DNS queries for records that this server cannot resolve.

Here I have listed the two DNS servers of my ISP and the Google DNS IP address.

Author Comment

ID: 39707847
Just to add, what I just noted.
We have 2 printers that I connected just through the IP address. When I've got this DNS issue on my server, the printer can not be reached by the clients via the IP address as well. (As I have deployed the printer through the server). It looks like all the clients cannot resolve any names as well when this happens.
LVL 78

Expert Comment

ID: 39707850
You may have other issues such as a virus that pounds your DNS server.

Use wireshark or network monitor to confirm that the DNS is being pounded.

Is your setup include the windows server functioning as a router?

Consider as a test removing the forwarders thus allowing your DNS server to go and retrieve data .....

Accepted Solution

dtwild earned 0 total points
ID: 39828726
I managed to find the issue.

I removed the RAS role from the server, restarted the server and the issue was resolved..
Thanks for all assistance in this matter guys, I am happy to see it working now.

Author Closing Comment

ID: 39841394
This resolved the issue, hopefully there are other users that have some benefit of this.

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