+ Post New Thread
Page 1 of 2 12 LastLast
Results 1 to 15 of 17
Wireless Networks Thread, Machines returning same IP address in Technical; Not sure how to explain this one, but we have about 250 machines on the network, but there are about ...
  1. #1
    tomscaper's Avatar
    Join Date
    Jul 2006
    Posts
    814
    Thank Post
    118
    Thanked 29 Times in 15 Posts
    Rep Power
    22

    Machines returning same IP address

    Not sure how to explain this one, but we have about 250 machines on the network, but there are about 4 or 5 machines that when i try to ping them by the computer name they return the same IP address.

    Hopefully this is something easy to resolve.

    Have attached screen shot of two computers i know about.
    Attached Images Attached Images
    Last edited by tomscaper; 30th April 2008 at 03:31 PM.

  2. #2
    Jona's Avatar
    Join Date
    May 2007
    Location
    Cranleigh
    Posts
    467
    Thank Post
    14
    Thanked 50 Times in 48 Posts
    Rep Power
    23
    Hmmm are these machines reporting IP conflicts at all? what happens if you do nslookup for both machines?

  3. #3

    SYSMAN_MK's Avatar
    Join Date
    Sep 2005
    Posts
    4,004
    Thank Post
    488
    Thanked 1,339 Times in 727 Posts
    Rep Power
    427
    I'd check the DNS entries on the server. I take it they have different IPs when you do ipconfig on the machines locally.

  4. Thanks to SYSMAN_MK from:

    tomscaper (1st May 2008)

  5. #4

    Geoff's Avatar
    Join Date
    Jun 2005
    Location
    Fylde, Lancs, UK.
    Posts
    11,802
    Thank Post
    110
    Thanked 583 Times in 504 Posts
    Blog Entries
    1
    Rep Power
    224
    Enable scavanging on your rDNS zone.

  6. Thanks to Geoff from:

    tomscaper (1st May 2008)

  7. #5
    tomscaper's Avatar
    Join Date
    Jul 2006
    Posts
    814
    Thank Post
    118
    Thanked 29 Times in 15 Posts
    Rep Power
    22
    Quote Originally Posted by SYSMAN_MK View Post
    I'd check the DNS entries on the server. I take it they have different IPs when you do ipconfig on the machines locally.
    Yes if i were to do ipconfig on the machine themselves it would bring up different IPs

    I am not sure how i would check the DNS entries on the server, any chance you could explain where to look.

    The computers themselves all work and connect, but for some reason i cant ping them by name.

  8. #6
    tomscaper's Avatar
    Join Date
    Jul 2006
    Posts
    814
    Thank Post
    118
    Thanked 29 Times in 15 Posts
    Rep Power
    22
    This is what nslookup reports

    Quote Originally Posted by Jona View Post
    Hmmm are these machines reporting IP conflicts at all? what happens if you do nslookup for both machines?
    Attached Images Attached Images

  9. #7

    Geoff's Avatar
    Join Date
    Jun 2005
    Location
    Fylde, Lancs, UK.
    Posts
    11,802
    Thank Post
    110
    Thanked 583 Times in 504 Posts
    Blog Entries
    1
    Rep Power
    224
    In the above examples, what are those two machines real IP addresses?

  10. #8
    tomscaper's Avatar
    Join Date
    Jul 2006
    Posts
    814
    Thank Post
    118
    Thanked 29 Times in 15 Posts
    Rep Power
    22
    staff-01 has 10.64.17.176
    res-13 has 10.64.17.68
    Quote Originally Posted by Geoff View Post
    In the above examples, what are those two machines real IP addresses?

  11. #9
    Unvalidated User
    Join Date
    Nov 2007
    Location
    the Pub
    Posts
    255
    Thank Post
    7
    Thanked 11 Times in 10 Posts
    Rep Power
    0
    I would firstly flush the local dns cache (ipconfig /flushdns)

    Then repeat what youve done. If it the same then goto the DNS management console on your server or wks (administrative tools->DNS) Look at your forward lookup zones, in the domain name you should see a list of A records. Look for the entry and see if they have repeats, you can delete them here. Then do an ipconfig /registerdns and they should reappear in the dns properly. If someone has added them manually there could also be a C Name record for example, just check the names.
    If this has happened then for it to work proper in the future the DNS scavenge needs to be switched on and setup with the right settings (as well as dhcp). Actually that reminds me about mine

  12. Thanks to blacksheep from:

    tomscaper (1st May 2008)

  13. #10
    Sirbendy's Avatar
    Join Date
    Nov 2005
    Posts
    2,298
    Thank Post
    8
    Thanked 202 Times in 153 Posts
    Rep Power
    109
    yep. IPCONFIG /FLUSHDNS.

    I end up doing it here sometimes..Netsupport does something similar on rare occasions..heh.

  14. Thanks to Sirbendy from:

    tomscaper (1st May 2008)

  15. #11
    FatBoy's Avatar
    Join Date
    Oct 2007
    Location
    Kent, UK
    Posts
    243
    Thank Post
    52
    Thanked 20 Times in 16 Posts
    Rep Power
    17
    We sometimes get duplicate entries in our DNS I guess because the machine aren't sometimes renamed or removed from the domain properly just delete the bad entires in DNS

    @ Geoff how would you enable scavanging on your rDNS zone and should this be something thats done on a LAN?

  16. Thanks to FatBoy from:

    tomscaper (1st May 2008)

  17. #12
    torledo's Avatar
    Join Date
    Oct 2007
    Posts
    2,928
    Thank Post
    168
    Thanked 155 Times in 126 Posts
    Rep Power
    47
    Quote Originally Posted by FatBoy View Post
    We sometimes get duplicate entries in our DNS I guess because the machine aren't sometimes renamed or removed from the domain properly just delete the bad entires in DNS

    @ Geoff how would you enable scavanging on your rDNS zone and should this be something thats done on a LAN?
    right click on the zone, and there's an option to set scavenging time or something like that. I believe the default is 14 days but You can then set the aging time in days to whatever you wish. There's also an option to scavenge resource records now, although can't remember if that's under rDNS options or somewhere else.

    We set scavenging to seven days and tried the scavenge now option...neither worked, so i think i'll have to just delete the duplicate records manually.

  18. Thanks to torledo from:

    tomscaper (1st May 2008)

  19. #13

    m25man's Avatar
    Join Date
    Oct 2005
    Location
    Romford, Essex
    Posts
    1,617
    Thank Post
    49
    Thanked 448 Times in 331 Posts
    Rep Power
    136
    Your scavenging period should be set to the duration of your DHCP leases.
    It's a common mistake to change DHCP lease durations without changing the DNS scavenging periods.
    This results in discrepancies in your DNS/DHCP databases with machines appearing to have the same or duplicate IP addresses in the DNS zone.
    Whilst this does not normally affect the client PC's themselves if they share files or printers, others will not be able to find them and Group Policies will regularly fail to apply on machines with multiple reverse DNS entries.

    Others have already correctly advised you how to set this.

    DNS DNS DNS, this is the core of Windows AD get this right and the rest is like falling off a log!
    Get it wrong and your AD will eventually die, along with your reputation.

  20. 2 Thanks to m25man:

    tomscaper (1st May 2008), torledo (30th April 2008)

  21. #14
    FatBoy's Avatar
    Join Date
    Oct 2007
    Location
    Kent, UK
    Posts
    243
    Thank Post
    52
    Thanked 20 Times in 16 Posts
    Rep Power
    17

    Lightbulb

    Ours is set to 8 days but I think it's got a lot to d with how many clients you have and what sort of DHCP range size you have set.

    Also FYI I was looking around some of are settings and if you right click on your Scope in DHCP and go to properties, then the DNS tab and under here you have "Enable DNS dynamic updates according to the setting below". Ours was set to only update if the clients requests it so I have now changed it to "Always dynamically update DNS A nad PTR records"


  22. Thanks to FatBoy from:

    tomscaper (1st May 2008)

  23. #15

    tmcd35's Avatar
    Join Date
    Jul 2005
    Location
    Norfolk
    Posts
    5,575
    Thank Post
    834
    Thanked 873 Times in 726 Posts
    Blog Entries
    9
    Rep Power
    324
    Quote Originally Posted by m25man View Post
    Your scavenging period should be set to the duration of your DHCP leases.
    It's a common mistake to change DHCP lease durations without changing the DNS scavenging periods.
    This results in discrepancies in your DNS/DHCP databases with machines appearing to have the same or duplicate IP addresses in the DNS zone.
    Whilst this does not normally affect the client PC's themselves if they share files or printers, others will not be able to find them and Group Policies will regularly fail to apply on machines with multiple reverse DNS entries.

    Others have already correctly advised you how to set this.

    DNS DNS DNS, this is the core of Windows AD get this right and the rest is like falling off a log!
    Get it wrong and your AD will eventually die, along with your reputation.
    Have some rep! just checked my settings, way off - explains the odd discrepancy I've seen bit like the OP. All changed now

SHARE:
+ Post New Thread
Page 1 of 2 12 LastLast

Similar Threads

  1. Research Machines
    By KeithFermor in forum Bad Experiences
    Replies: 46
    Last Post: 30th November 2007, 02:52 PM
  2. Virtual Machines
    By FN-GM in forum *nix
    Replies: 4
    Last Post: 4th October 2007, 06:55 PM
  3. Citrix on old machines
    By adamyoung in forum Thin Client and Virtual Machines
    Replies: 8
    Last Post: 2nd October 2006, 09:35 AM
  4. RM machines
    By witch in forum Hardware
    Replies: 11
    Last Post: 14th June 2006, 11:25 AM

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •