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Windows Thread, DNS problems that are confusing. in Technical; I have a DNS issue again, I think i have mentioned this before to you that we use a piece ...
  1. #1
    tosca925's Avatar
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    DNS problems that are confusing.

    I have a DNS issue again, I think i have mentioned this before to you that
    we use a piece of software called VNC which is used to remotley monitor
    any machine in the school. We access this by typing the machine name in a
    log in box to view the screen. Trouble is that we type the machine and get
    another one instead. Over the last 12 months i must have recreated the DNS
    records 6 times because of this. I have just had a issue today the same, i
    checked the ip of the pc and it points to a different pc. I check the DNS
    records and there was two records for the same ip address, which both
    pointed to the two pc's in question. I have maually deleted the record of
    the wrong pc.

    If I'm honest DNS & DHCP still confuse me a little at times, have you any idea what could be causing this?

    Is there a way to remove double entrys?
    Is correct procedure to remove manually ? any tips please?

    I have scavenged the stale records and change aging the time to 1 day from the default of 7.

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    Geoff's Avatar
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    Re: DNS problems that are confusing.

    Its the client machines job to update the DNS. The 'new' machine with the IP obviously isn't doing this. Its probably broken in some non-obvious way. Best go check it out and run netdiag on it.

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    tosca925's Avatar
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    Re: DNS problems that are confusing.

    I checked my DNS A recordes and i had up 3 pc's all having the same ip address record.

    Can you manually delete these records witjout causing any problems?

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    GrumbleDook's Avatar
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    Re: DNS problems that are confusing.

    Stage 1: yep ... get rid of old ip addresses ... if it comes from dhcp then wait until all machines are shut down at the end of the day and delete what you don't need. At the same time release all addresses in your DHCP so that you start afresh the next day

    Stage 2: in your DHCP make reservations for every machine. DHCP is good and handy, but it is nice to know that machine z has IP of x.x.x.x ... it is also handy for ironing out issues like the above. I am sure that Spot has got a script for this ... I will nudge him and get him to PM stuff to you ... once you are happy then post it back to the forum. (his stuff can be a little rough and ready at times so it would be nice to have someone clean it up ...)

    Stage 3: Buy the following book. It is a must. DNS on Windows 2003 Server By Cricket Liu, Matt Larson and Robbie Allen (http://www.oreilly.com/catalog/dnswinsvr/) ... if you can also get hold of a copy of DNS and BIND By Paul Albitz & Cricket Liu (http://www.oreilly.com/catalog/dns4/) and go through that first, it will help you understand DNS ... and then the windows book will explain who the flip to make it work in an AD environment so other things can use it too.

    Stage 4: Go and have a well earned pint.

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    DMcCoy's Avatar
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    Re: DNS problems that are confusing.

    You can also turn on scavenging of old records on in dns, this will help to keep that tidy, and an expiry of 8 days or so for that and dhcp will keep stuff up to date.

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    mark's Avatar
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    Re: DNS problems that are confusing.

    DHCP reservations cured all my VNC/VNCcon woes. That is what makes VNC happy.

    Shame we changed IP ranges so I have to do it all again!

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    ChrisH's Avatar
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    Re: DNS problems that are confusing.

    Use a netsh script makes life a lot easier.

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    Re: DNS problems that are confusing.

    Have you tried running ipconfig /flushdns on your local pc? as far as i know, this will make you pc check the DNS server properly again.

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    Re: DNS problems that are confusing.

    Thats no use if the DNS server has multiple entries for the same IP Address though. The client will use whichever the DNS server returns to it first whether it has a local DNS cache or not.

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    Re: DNS problems that are confusing.

    Can't you use the NETBIOS name in the VNC viewer rather than the IP address?

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    Re: DNS problems that are confusing.

    My bad- you were doing that anyway!

    I would certainly look at lease times and flushing the DNS then re-registering the station as suggested above. Works for us. Of course if you find that you do have multiple entries for the same name (i.e. more than one IP per name for some reason), the route to go would be reservations (as Tony suggested). In point of fact that may be the best route to go if you are having issues across the board with DHCP and DNS.

    Apologies.

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    Re: DNS problems that are confusing.

    Going to say it again. Scavenging. This is what its for!

    http://technet2.microsoft.com/Window...4c4f41033.mspx

    It removes old ddns entries (leaves static ones alone - no timestamp).

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    Re: DNS problems that are confusing.

    You can also set your DHCP server to manage the DNS registration rather than leaving it to the (possibly broken) clients.

    In your DHCP server go to the Scope Properties Dialog and then to the DNS tab. Enable:

    1. Enable Dynamic DNS Updates
    2. Always dynamically update DNS A and PTR records.
    3. Discard A and PTR records when a lease is deleted

    Make sure you have a reverse lookup zone in your DNS server for your IP range too. I've seen that cause wierdness.

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    Re: DNS problems that are confusing.

    I'm glad you said it before I did.

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