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DNS / DHCP Issues in Server 2008R2 Domain RRS feed

  • Question

  • Hi folks,

    We’ve been having an ongoing issue for a while now in that some PCs and laptops (Win 7) in our company can’t be contacted by hostname i.e. if we try and RDP from one Windows 7 PC to another the RDP session fails as if the PC isn’t turned on, but it is indeed turned on and connected to the network. 

    Even if we ping the host name of a particular computer that is on it fails to reply but if I go into DHCP I can find the hostname bit it has a different IP address assigned to it other than what is listed in DNS for that host name.

    So for some reason when some computers get switched on and be allocated a new dynamic IP address through DHCP the corresponding record in DNS doesn’t seem to get updated meaning we need to go into DNS and manually amend the Host A record with the new IP address that it has been given so we can RDP onto that computer using the hostname.

    At present aging and scavenging isn’t enabled in our environment as we are afraid to in case it removes live DNS entries that just haven’t been turned on in a wee while.  Does aging and scavenging just ignore static DNS entires and does aging and scavenging work in DHCP as well?

    One other thing I noticed is that if I delete an incorrect DNS Host A record and create it manually and assign the hostname and the correct IP address it says static rather than having a timestamp on it. When I create the new record I always click on our domain in the Forward Lookup Zone and on creation I always select Create the associated pointer (PTR) record so not sure why the manual record doesn’t get a time stand.

    So any help/advice or suggestions would be greatly appreciated.

    Thanks,

    Bonemister

    Friday, January 31, 2014 3:53 PM

All replies

  • Does aging and scavenging just ignore static DNS entires...

    Yes

    and does aging and scavenging work in DHCP as well?

    No - but old leases are removed when the lease expires - same concept (expired record/entry/lease), different mechanism.

    Technically, I believe manually added (static) records *do* have a timestamp but the value is "0" and is not aged (or scavenged).

    Taking into account the caution recommended in the article below, you probably want to consider scavenging. Since I don't know your environment I won't just say "Do it".

    http://technet.microsoft.com/en-us/library/cc771677.aspx


    Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you.

    Friday, January 31, 2014 4:41 PM
  • As for clients not registering in DNS, what do your settings look like here?

    http://technet.microsoft.com/en-us/library/Ee692588.05atnc02_big(l=en-us).gif

    And your DHCP server settings here? -> see the image of the DHCP server settings, the discussion itself may help too:

    http://social.technet.microsoft.com/Forums/en-US/35cf1bbd-247d-425e-a54f-c536670e9abd/some-computers-keep-old-ip-addresses?forum=winserverNIS


    Please mark as helpful if you find my contribution useful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you.

    Friday, January 31, 2014 4:52 PM
  • Hi David,

    Thanks for your reply and for clarifying those things for me.  Unfortunately in my workplace when I add a manual DNS Host A record it does become a static entry and doesn't have the '0' you mention, do you have any idea why that would be as I'm worried about it affecting things if I were to enable aging and scavenging.

    Is it possible to just enable aging and have it remove entries before a time of my choosing or does scavenging need to be enabled also?

    I still can't understand why the relationship between DHCP and DNS isn't working correctly. Sure if DNS has an A record for a computer and the IP address changes via DHCP there is bound to be a way to setup DNS to be able to update the records it holds - do you know if my reading of this is correct.

    By the way, I can confirm that my adapters TCP/IP DNS settings are the same on of the PCs that had the DNS fault as in your screenshot the only different is we have the tick in Append parent suffixes... - would that make a difference.

    Thanks also for that other link, it seems very interesting and I'll have a good read through it carefully before doing anything!!

    Thanks again for you reply and I look forward to seeing any responses.

    Regards,

    Bonemister


    • Edited by bonemister Friday, January 31, 2014 7:07 PM
    Friday, January 31, 2014 6:44 PM
  • Hi,

    Have you enabled secure dynamic update?

    If yes, I suggest you place DHCP server to the DNSUpdateProxy group to see if it works.

    More information for you:

    Secure Dynamic Update

    http://technet.microsoft.com/en-us/library/cc961412.aspx

    Don't be afraid of DNS Scavenging. Just be patient

    http://blogs.technet.com/b/networking/archive/2008/03/19/don-t-be-afraid-of-dns-scavenging-just-be-patient.aspx

    Best Regards,

    Amy Wang

    Tuesday, February 4, 2014 8:28 AM
    Moderator
  • Hi Amy,

    Thanks for your advice!

    We have now gone ahead and enabled scavenging and it seems to have worked well as there aren’t any old entries now showing in DNS.  I also placed the DHCP server in the DNSUpdateProxy and so far so good.

    My problem is our issue from the original post is still happening i.e. The DNS Host A record isn’t getting updated so we still have the problem intermittently that we can’t RDP onto a Win 7 PC by host name or if we ping the hostname it appears to be down when it isn't, it just has got a different IP address.

    If a computer isn’t connected to the network for a while or moves to a different site with a different DHCP range, DNS doesn’t seem to take account of the new IP address that the computer has and doesn't update the DNS Host A record.

    Would anyone have any ideas why that would be and would you have any idea how I can best fault-find the issue and more importantly know how to resolve the problem.

    Thanks again for all of your help thus far and here’s hoping some kind person or persons will help me get to the bottom of this very frustrating issue.

    Thanks,

    Bonemister

    Wednesday, February 26, 2014 11:52 AM