Prevent network adapter from automatically registering in DNS

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Hello,

I have, in my Windows Server 2012 R2 server, two network adapters. One is used for normal networking, the other is connected to a Hyper-V switch to accommodate several virtual machines. Windows requires me to assign an ip address to this virtual switch, although, IMHO, it does not need one. What is more, this ip address causes troubles. I have disabled automatic registration of this address in DNS, but this seems to be ignored. This address appears in DNS anyway.

The result is, that my server is known in DNS by two addresses.

Because of the automatic round-robin selection of the two addresses, about 50% of the time I get the undesired address. Sometimes this address works, but most of the time it does not. I am not sure why not. Maybe because this adapter is busy enough with other work.

Manually removing this unwanted address from DNS does not help, because shortly afterwards it just reappears.

Anyone knows how to really disable the automatic DNS registration?

TIA,

Bart

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Your machine has two network adapters on the same network so you must have two IP addresses and two DNS entries. No way around that.
You could remove one of the adapters and run your VMs through the other. There is no downside apart from a little more traffic, but if it’s a Gb port you won’t notice.

Re-reading your post it may be the second adapter is not connected to the network. If that is the case, why do you have it?

cheers, Paul

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Your machine has two network adapters on the same network so you must have two IP addresses and two DNS entries. No way around that.
You could remove one of the adapters and run your VMs through the other. There is no downside apart from a little more traffic, but if it’s a Gb port you won’t notice.

Re-reading your post it may be the second adapter is not connected to the network. If that is the case, why do you have it?

cheers, Paul

Thanks for your response.

I am from the IT generation when the OSI network model was developed, and not everything was IP. So I know that something can be connected to the network, but does not ever send or receive IP packets. The Hyper-V switch itself is such a device, and it could therefore live without an IP address. And even if it has an IP address, it could certainly live without a corresponding DNS entry.

But I understand that these days, everything *IS* IP. So I will take your advice, and remove the second adapter.

However, why is the option to not register the IP address of an adapter ignored? It is there (and it still is there in Windows Server 2016), but it is redundant.

Regards,

Bart

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Normally second adapters are “teamed” to provide increased throughput and reliability. Having them independent implies they are to be connected to different networks. If you leave the second adapter disconnected and give it an address on a different network you should not see additional DNS entries.

cheers, Paul

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Yes, I understand that.

But:

– Unfortunately, I cannot afford the extra hardware for a second network
– I want the virtual machines to have network connectivity, so the second adapter must be connected

So removing the second adapter and tying the Hyper-V switch to the first will solve this problem.

But I am still convinced that this problem should not exist in the first place. There is absolutely no need to have every IP address in DNS. Windows does not give me this option, so I blame Windows.

Bart

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You can use the second network adapter for just the Hyper-V switch and not the host OS – I think this is what you’re trying to achieve. Open Hyper-V Manager then click on the Virtual Switch manager. Select your virtual switch and you’ll see that it’s connected to the External network and you should have your second LAN adapter selected in the drop-down. Underneath that is a check-box called ‘Allow management operating system to share this network adapter’. Untick this box and you’ll find that the host OS can no longer see the second LAN adapter so it won’t have an IP address. It will just allow your VMs to connect to the physical LAN. As far as the OSI model is concerned, this hides the physical layer of the second NIC from the host OS. I’m very old too…

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Not Windows fault that you have two adapters where only one is required. 🙂

cheers, Paul

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You can use the second network adapter for just the Hyper-V switch and not the host OS – I think this is what you’re trying to achieve.

Open Hyper-V Manager then click on the Virtual Switch manager. Select your virtual switch and you’ll see that it’s connected to the External network and you should have your second LAN adapter selected in the drop-down. Underneath that is a check-box called ‘Allow management operating system to share this network adapter’. Untick this box and you’ll find that the host OS can no longer see the second LAN adapter so it won’t have an IP address. It will just allow your VMs to connect to the physical LAN.

As far as the OSI model is concerned, this hides the physical layer of the second NIC from the host OS. I’m very old too…

Reply | Quote

You can use the second network adapter for just the Hyper-V switch and not the host OS – I think this is what you’re trying to achieve.

Open Hyper-V Manager then click on the Virtual Switch manager. Select your virtual switch and you’ll see that it’s connected to the External network and you should have your second LAN adapter selected in the drop-down. Underneath that is a check-box called ‘Allow management operating system to share this network adapter’. Untick this box and you’ll find that the host OS can no longer see the second LAN adapter so it won’t have an IP address. It will just allow your VMs to connect to the physical LAN.

As far as the OSI model is concerned, this hides the physical layer of the second NIC from the host OS. I’m very old too…

Yes! This is what I was looking for! And I didn’t even have to reboot Windows!

It’s sad that modern day Windows and network admins don’t know what the OSI model stands for. By the way, I was an OpenVMS system specialist.

Thank you, and regards,

Bart

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I know you received the answer you were looking for, but I thought I’d add my two cents.
There are occasions where there must be multiple NICs and, as you’ve discovered, Windows wants to register both (or all) of them in DNS.
You can stop this behavior by setting this registry value.
“DisableDynamicUpdate”=dword:00000001
in this registry key.
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces{The NIC you want to be quiet}

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I know you received the answer you were looking for, but I thought I’d add my two cents.
There are occasions where there must be multiple NICs and, as you’ve discovered, Windows wants to register both (or all) of them in DNS.
You can stop this behavior by setting this registry value.
“DisableDynamicUpdate”=dword:00000001
in this registry key.
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParametersInterfaces{The NIC you want to be quiet}

Thanks, but as far as I know, this is what the setting “Register this connection’s settings in DNS” does. And it is ignored by Windows.

I agree that the solution given above is not really the solution that I was asking for, but it suits me well!

Regards,

Bart

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