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Thread: DNS: multiple hosts listed with duplicate IP addresses

  1. #1
    Chris H Guest

    DNS: multiple hosts listed with duplicate IP addresses

    Hey Guys,

    I was wondering, in my internal DNS tables, running Windows 2003 Server
    and Dynamic addressing, I see that I have multiple hosts listed with
    duplicate IP addresses...

    This is in my forward lookup zone in DNS:

    Name Type Data
    NY-1 Host (A) 192.168.0.181
    NY-2 Host (A) 192.168.0.181
    MA-2 Host (A) 192.168.0.181
    CT-5 Host (A) 192.168.0.181
    .... among all the other IPs listed...

    I have this many times...

    So when I do an NSLOOKUP for an IP, I may not get any one of those
    hosts listed...

    Is there a way to force DNS to remove the oldest used and force an
    update? perhaps daily?

    Is that what Scanvenging is for?

    Any help would be MUCH apprciated... Thank you in advance.


  2. #2
    Herb Martin Guest

    Re: multiple hosts listed with duplicate IP addresses


    "Chris H" <Christopher.Hoche@gmail.com> wrote in message
    news:1169697480.490201.289620@k78g2000cwa.googlegroups.com...
    > Hey Guys,
    >
    > I was wondering, in my internal DNS tables, running Windows 2003 Server
    > and Dynamic addressing, I see that I have multiple hosts listed with
    > duplicate IP addresses...
    >
    > This is in my forward lookup zone in DNS:
    >
    > Name Type Data
    > NY-1 Host (A) 192.168.0.181
    > NY-2 Host (A) 192.168.0.181
    > MA-2 Host (A) 192.168.0.181
    > CT-5 Host (A) 192.168.0.181
    > ... among all the other IPs listed...
    >
    > I have this many times...
    >
    > So when I do an NSLOOKUP for an IP, I may not get any one of those
    > hosts listed...


    Reverse lookups come from the PTR records in the REVERSE zone --
    generally you can only have one of those per IP (that is effective.)

    > Is there a way to force DNS to remove the oldest used and force an
    > update? perhaps daily?
    >
    > Is that what Scanvenging is for?


    Not exactly since scavenging requires the record to first expire -- it
    will remove them, but not just because there is another record being
    added.

    Use DHCP to do the registration when machines share addresses like
    this (such addresses such be managed by DHCP anyway) and check
    the boxes so that it also removes the PTR by expiration.

    > Any help would be MUCH apprciated... Thank you in advance.
    >




  3. #3
    Chris H Guest

    Re: multiple hosts listed with duplicate IP addresses

    Thanks for ths info...

    So if I go to my DNS and the properties of my server.domainname.com,
    then go to the DNS tab,

    should I have a check mark in the: Enable DNS dynamic updates according
    to the settings below:

    Always dynamically update DNS A and PTR records?

    or

    Dynamically update DNS A and PTR records only if requested by the DHCP
    clients?

    THEN, I have a check in:

    Discard A and PTR records when lease is deleted.

    Thanks in advance.


  4. #4
    Herb Martin Guest

    Re: multiple hosts listed with duplicate IP addresses


    "Chris H" <Christopher.Hoche@gmail.com> wrote in message
    news:1169728489.627094.42280@s48g2000cws.googlegroups.com...
    > Thanks for ths info...
    >
    > So if I go to my DNS and the properties of my server.domainname.com,
    > then go to the DNS tab,
    > should I have a check mark in the: Enable DNS dynamic updates according
    > to the settings below:
    >
    > Always dynamically update DNS A and PTR records?


    I vote for this -- gives the entire job to the DHCP server.

    Also check the one for legacy clients if you have (any chance of having)
    any of those.

    > or
    > Dynamically update DNS A and PTR records only if requested by the DHCP
    > clients?
    >
    > THEN, I have a check in:
    >
    > Discard A and PTR records when lease is deleted.


    YES.




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