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Windows Thread, Odd DNS problem in Technical; Was just running Angry IP Scanner to grab the MAC addresses of some new PCs yesterday but started feeling rather ...
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    gshaw's Avatar
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    Question Odd DNS problem

    Was just running Angry IP Scanner to grab the MAC addresses of some new PCs yesterday but started feeling rather when none of them showed up in the list. Did a quick ipconfig and the IP addresses were right but the name resolution completely wrong! In the end it was showing as if there were 2 computers with the same IP responding yet I could see that there weren't any conflicts.

    Checked DHCP and leases were fine, went to DNS and then the problem showed!

    Each IP had 2-3 A records associated with it! So basically I had...

    10.x.x.145 - Room21 (A)
    10.x.x.145 - Room14 (A)

    And so on. Event Viewer has no errors since Jan (when I fixed a metadata cleanup from a dead DC)

    It's AD integrated DNS, 2 DNS servers (1 on the DC, one on another server). That's been setup ages, maybe it's wrong?

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    Diello's Avatar
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    Have you got DNS scavenging enabled?

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    gshaw's Avatar
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    Doesn't seem like it, I'm guessing it therefore isn't removing old records once they're no longer valid?

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    Geoff's Avatar
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    Yes. You can check if that's happening by looking in your rDNS zone and sorting the display by the hostname column.

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    SpuffMonkey's Avatar
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    You can get this happening if you re-Ghost Pcs with a new SSID - they lose permissions on the existing DNS record and can't refresh it.

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    bizzel's Avatar
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    To avoid duplication, take a look at my post here for checking and enabling scavenging.

    http://www.edugeek.net/forums/146909-post7.html

  7. Thanks to bizzel from:

    gshaw (1st May 2008)

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    Geoff's Avatar
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    Quote Originally Posted by SpuffMonkey View Post
    You can get this happening if you re-Ghost Pcs with a new SSID - they lose permissions on the existing DNS record and can't refresh it.
    You can allow non-secure updates and get round this problem. You would want to do this anyway in a mixed environment otherwise non-windows machines will not be able to register themselves in dns.

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    gshaw's Avatar
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    Thanks for the link Bizzel, never knew there were that many boxes to tick to enable it - will try that soon, leases are set at 8 days so will your settings from the linked post be OK?

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    > leases are set at 8 days so will your settings from the linked post be OK?

    That relationship is quite complicated, but doesn't matter too much unless you're seriously bothered about replication traffic. IIRC 8 days is the default DHCP lease, so stick with the defaults for DNS scavenging.

    Very key point: If you have any manually added DNS RR's then make sure scavenging is turned off on the properties of those particular records.
    Last edited by PiqueABoo; 1st May 2008 at 07:47 PM. Reason: typos

  11. Thanks to PiqueABoo from:

    gshaw (2nd May 2008)

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    gshaw's Avatar
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    Dredging up an old thread but enabled scavenging today as per the instructions above but keeping getting a 2502 event "Event ID 2502 - "A scavenging cycle has just been completed however no nodes were visited".

    Went through Google and found that I needed to check "The Zone can be Scavenged after" date, as sometimes you have to wait for that interval to pass before scavenging. However mine is set to 01\01\1601 00:00:00 )

    The reverse zone is fine and has 3rd August as the date, which makes sense but why is the forward zone gone all weird

    EDIT: just tried reloading the zone and that seems to have done it... very odd!

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    Geoff's Avatar
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    DNS stores it's data in a Jet database. This isn't exactly the most reliable of database engines.

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