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DNS resolver not honoring interface metrics

    Question

  • There are already a lot of threads about which DNS Server gets used if there are multiple NICs/VPN connections. From what I learned from those, the DNS server of the preferred adapter will always be used first. So that must be the one with the lowest metric value, right?

    My configuration:

    1 physical NIC

    2 virtual VPN adaptors

    I always want to use the DNS server which the physical NIC got via DHCP. All three adapters had an automatically assigned metric value of '20'. So I set the metric of the physical interface to '1'. The two VPN adapters stayed on Automatic Metric which was still '20'. Now I would have assumed that every DNS query from that moment on would use the server of the physical NIC but that wasn't always the case. In fact when I set the metric back to automatic, then the desired DNS server was used, although all three interfaces were back to a metric of '20'.

    So, I assume that there must be other factors that are considered by the system when choosing which DNS server will be used first for the next query. Is that right?

    Tuesday, December 19, 2017 12:14 PM

All replies

  • Hi,

    As I understand, the question is that the costumer has a physical NIC and two VPN, then he change the metric of the interface, but when he testes he find that it seems to be not useful?

    According to my understanding and researches, when we configure DNS address in DHCP scope, it will choose the first one DNS server to use.

    In addition, we can find the binding order, which is stored in the registry in the following location: 

    HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Linkage\Bind. <o:p>

    The list includes all the device GUIDs for network adapters and active connections in the binding priority order. You can change order of the GUIDs in the registry does impact the binding order, including for VPN connections.

    You can refer to the following link: https://serverfault.com/questions/356115/vpn-connection-causes-dns-to-use-wrong-dns-server

    Note: this is a 3rd party link, we don't have any warranties on this website. It's just for your convenience. 

    If you have any questions or requirements, please feel free to let me know.


    Please remember to mark the replies as answers if they help.
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    Thursday, December 21, 2017 8:50 AM
  • Hi,

    What is going on?

    If you have further problems, feel free to contact me.


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Friday, December 22, 2017 5:51 AM
  • Hi,

    sorry for the late reply.

    I already tried to set the binding order, too. But it had no effect which is why I changed the interface metrics in the first place.

    Wednesday, January 03, 2018 9:19 PM
  • Hi,

    To know more information about the problem, I have a few things that should confirm with you:

    1.How many DHCP scope do you have?

    2.What is the DNS ip address in each DHCP scope?

    3.If the IP address of the DNS physical NIC can be set to static, you can test to configure it as a static one.


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Thursday, January 04, 2018 6:10 AM
  • Hi,

    Any updates?


    Please remember to mark the replies as answers if they help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Monday, January 08, 2018 2:21 AM