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IPv4 DNS registatrations sometimes disapeering while IPv6 stay (on some clients)

    Question

  • Hi, we use Windows 10 (1803) as clients and Windows 2016 as DC, DNS and DHCP server.
    A few weeks ago we started to implement IPv6 in our internal networks, but run into some problems.

    for IPv4 we use DHCP to assign IP and DNS Servers
    for IPv6 we use SLAAC with the other config flag, so DHCPv6 is only used to assign DNS Servers

    for IPv6, this works fine, hosts register themselfs at the Server without a problem
    for IPv4, the server registers the client, but than the client sents a update and remove the A entry

    I already did some DNS debug logging and see the following: 

    1. DHCP Server updates A with IP
    2. DHCP Server updates PTR (v4)
    3. DHCP Server updates A with IP
    4. DHCP Server updates PTR (v4)
    5. Client updates A and AAAA
    6. Client updates IPv6 PTR
    7. Client updates IPv6 PTR 
    8. Client updates IPv4 PTR 
    9. Client updates A and AAAA, but A is empty and gets deleted
    10. Client updates IPv6 PTR, but IPv4 PTR is empty and gets deleted

    each time QUESTION and RESPONSE were send via IPv4
    the time between first and last log entry were 8 seconds, so this happens fast 

    It only happens on a few clients which are in different departments and vlans , about 5 to 10 per day out of 400 Clients

    I also looked at the debug log for clients who don´t have this problem and I see that these clients update A and AAAA themself (same vlan as the other client).

    Does someone have an idea whats going wrong?

    Andreas


     
    Wednesday, July 25, 2018 12:17 PM

Answers

  • Hi,

    I finaly solved the problem.
    I removed the "other config flag" and the "ipv6 dhcp relay" addresses from the interface of the router.
    Now it works as expected.

    The clients now get:

    IPv4
    IP  --> DHCP
    DNS --> DHCP

    IPv6 
    IP  --> SLAAC
    DNS --> ----


    I think the Problem was, Windows tryed to register at the IPv4 DNS Server with IPv4 and IPv6 and (maybe) on the IPv6 DNS Server only with it´s IPv6 Address. 
    Since the DNS Servers for IPv4 and IPv6 are the same hosts for in this envirement this seams to cause an error.
    But it seems that there is an race condition and only happens, if the DHCP server answers slower or faster than usal or the client takes longer to decide whats his IPv6 address for this subnet.

    Best regards,

    Andreas



    • Marked as answer by awen-1981 Thursday, May 9, 2019 9:16 AM
    • Edited by awen-1981 Thursday, May 9, 2019 9:18 AM
    Thursday, May 9, 2019 9:16 AM

All replies

  • Hi,

    Thanks for your question.

    This problem occurs if Option 81 is defined and ISATAP or 6to4 interfaces are present. DNS dynamic update protocol update incorrectly sets TTL to 0 which triggers record deletion for IPv6 record registration. 

    Please refer to the link below:

    https://support.microsoft.com/en-in/help/2985877/cumulative-list-of-reasons-that-dns-records-disappear-from-dns-zones 

    Best regards,

    Travis


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    Thursday, July 26, 2018 3:17 AM
    Moderator
  • Hi,
    thanks for the answer, but this did not help.
    I checked the hosts who unregistered there IPv4 address, none of them had ISATAP vs 6to4 enabled.


    Best regards

    Andreas

    Monday, July 30, 2018 1:25 PM
  • Hi,

    Thanks for your reply.

    Please check the Always dynamically update DNS reords of scope properties. 

    From the  DNS debugging log, the client updates both the A and AAAA records, but DHCP should register the A record instead of the client.

    Best regards,

    Travis


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    Tuesday, July 31, 2018 9:26 AM
    Moderator
  • Hi, 

    a few days before I opend this thread, we changed this setting from "Always dynamically ..." to "Dynamically update DNS records ..." and hoped that would fix the problem.

    As you said, the DHCP should update the A record, and so he does.
    But a few momets later, the client registers his addresses (A and AAAA) and does it again and removes the A entry.

    best regards,

    Andreas

    Wednesday, August 1, 2018 7:26 AM
  • Hi,

    Thanks for your reply.

    Maybe we should try to let the clients to register IPv4 and IPv6 DNS records by themselves.

    Best regards,

    Travis


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

    Thursday, August 2, 2018 8:06 AM
    Moderator
  • Hi,

    Was your issue resolved?

    If you resolved it using our solution, please "mark it as answer" to help other community members find the helpful reply quickly.

    If you resolve it using your own solution, please share your experience and solution here. It will be very beneficial for other community members who have similar questions.

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    Best Regards,

    Travis


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    Friday, August 3, 2018 9:15 AM
    Moderator
  • Hi,

    I finaly solved the problem.
    I removed the "other config flag" and the "ipv6 dhcp relay" addresses from the interface of the router.
    Now it works as expected.

    The clients now get:

    IPv4
    IP  --> DHCP
    DNS --> DHCP

    IPv6 
    IP  --> SLAAC
    DNS --> ----


    I think the Problem was, Windows tryed to register at the IPv4 DNS Server with IPv4 and IPv6 and (maybe) on the IPv6 DNS Server only with it´s IPv6 Address. 
    Since the DNS Servers for IPv4 and IPv6 are the same hosts for in this envirement this seams to cause an error.
    But it seems that there is an race condition and only happens, if the DHCP server answers slower or faster than usal or the client takes longer to decide whats his IPv6 address for this subnet.

    Best regards,

    Andreas



    • Marked as answer by awen-1981 Thursday, May 9, 2019 9:16 AM
    • Edited by awen-1981 Thursday, May 9, 2019 9:18 AM
    Thursday, May 9, 2019 9:16 AM