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Thousands of DNS Update Requests at Once RRS feed

  • Question

  • We are running two DHCP servers in hot-standby functioning normally with DNS Dynamic Update and Name Protection enabled. Everything seems to be working normally, DHCP requests and DNS updates roll in every second or so and they work fine. But occasionally a huge block of DNS Update requests come in, thousands of requests with the same timestamp which immediately fills the queue and the DNS updates begin to fail because the queue is full.  Has anyone seen this behavior before?
    Tuesday, June 26, 2018 4:50 PM

All replies

  • Hi,

    Thanks for your question.

    Please try the following suggestions to see if it could be of help.

    This seems to be related to the dynamic update of DNS. The DHCP server uses the queue limit to restrict the number of DNS records that the server tries to unregister at the same time. If there are lots of pointer (PTR) resource records to be scavenged, the DHCP server may reach the queue limit. Refer to the following link:

    https://support.microsoft.com/en-sg/help/932464/how-dns-dynamic-updates-work-together-with-the-dns-aging-and-scavengin

    you can use a registry value to set the queue limit. To set the queue limit, follow these steps:

    1. Click Start, and then click Run.
    2. Type regedit in the Open box, and then click OK.
    3. Locate the following registry subkey:

    HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DhcpServer\Parameters

    1. Right-click Parameters, point to New, and then click DWORD Value.
    2. Type DynamicDNSQueueLength for the value name, and then press ENTER.
    3. Double-click DynamicDNSQueueLength, and then type a value for the queue limit. For example, type 2048.  Note In Windows Server 2008 and Windows Server 2008 R2, the value of DynamicDNSQueueLength can be up to 65536.
    4. Quit Registry Editor.
    5. Click Start, point to Administrative Tools, and then click Services.
    6. Stop and then restart the DHCP Server service.

    Refer to the following link:

    https://support.microsoft.com/en-us/help/837061/dhcp-server-processes-expired-ptr-resource-records-in-windows-server-2

    Hope you have a nice day!

    Best regards,

    Travis


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    Wednesday, June 27, 2018 2:56 AM
  • I haven't made those changes yet but oddly enough, shutting down the fail over server seems to have resolved this issue. Why would a hot standby server do this?
    Wednesday, June 27, 2018 1:55 PM
  • Hi,

    Thanks for your reply.

    I don't think this issue has anything to do with failover. When the queue limit is reached, remaining records are not processed until the next registration interval. This means that expired records will be updated at a specific time.

    The hot standby server services the clients, only in event of active server being down. The clients fallback to the active server once the active server becomes available again post the outage.

    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, June 28, 2018 2:16 AM