Hi, Setup: physical hardware: Dell T300 server, dual nic interface software: windows 2008 r2 server Configuration: the above hardware runs a virtual machine via hyper-v. This VM runs windows server 2008 R2 and exchange 2010; it is the only domain controller in a domain. One of the NICS on the pohysical hardware is designated as the virtual network adaptor. Problem: using DNS on the physical server appears to work fine, but using it on the virtual server does not. The symptom is a failure to find any external site on the first attempt. On the second attempt it works. I'm guessing that, byt the time of the 2nd attempt, it has got the details and cached them. This problem affects all clients as they all use this dns on the server The VM has the dns configured with the same forwarder as the physical system so that should not be an issue. I think it must be a timing issue of some sort but increasing the timeout to the forwarder does not make any difference. NSLOOKUP shows that it is trying to get an AAAA record as well as an A record (AAAA being the IPV6 equivalent of A) as the interface has IPV6 enabled (has to be there apparently or other things dont work). I would be grateful for any suggestions as this is seriously holding up deployment of a new server into production. PS I should add that DNS lookups work perfectly, and fast, on the physical server and all other machines in our environment. The problem seems related to its use in the virtual environment

Hi, Thanks for posting here. Is this virtual domain controller using itself as primary DNS server ? and has configured to forwarder all domain name query requirements except AD domain to external DNS server ? I’d suggest trying following methods and check if this issue persist 1. Disable another physical NIC which VM not using. 2. Changing the MaxCacheTTL registry value to 2 days or greater with following workaround: Warning: Serious problems might occur if you modify the registry incorrectly by using Registry Editor or another method. These problems might require you to reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk. 1. Start Registry Editor (regedit.exe). 2. Locate the following registry key: 3. HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters 4. On the Edit menu, click New, click DWORD (32-bit) Value, and then add the following value: Value: MaxCacheTTL Data Type: DWORD Data value: 0x2A300 (172800 seconds in decimal, or 2 days) 5. Click OK. 6. Quit Registry Editor. 7. Restart the DNS Server service. Thanks. Tiger Li Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Thanks for the comment. I have disabled the NIC not being used for VM networking and updated the registry as specified. No difference. It takes several repeated tries for the nslookup to find a name To answer your query, the VM is using itself as the main dns server and is configured to use a forwarder for all non-local requests. For example: the VM NIC has an IP of 192.168.58.206 and the external dns is accessed via a router at 192.168.58.1 (clearly behind a network firewall hence the 192.168.x.y ip format!) So the vm NIC has its DNS configured to 192.168.58.206 and the DNS has its forwarder configured to 192.168.58.1 I suppose, in case its relevant, I should also mention that both physical and VM are using 64-bit windows server 2008 R2

try changing the DNS forward address to the ISP DNS that the 58.1 router actually uses, this would be a public address. Then also add 127.0.0.1 as a secondary dns address on the NIC of the VM (which is a domain controller with ad/DNS right?) Once done do an ipconfig /flushdns, then a /registerdns -Chad edit: it's a DC on a VM so be sure any hyperv time settings are disabled and it's getting NTP time from internet.