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Thread: Duplicate IPs

  1. #1
    Senior Member Blunted One's Avatar
    Join Date
    Dec 2005

    Angry Duplicate IPs

    Recently as well as in the not so recent past I have noticed that certain devices like the IP phones complain or stop working when a duplicate IP is detected. This also seems to happen ever so often with game consoles (since they are connected to the network too).

    Aside from this being quite annoying I was wondering how I can solve this issue once and for all.

    Would changing the settings in DNS so dynamic updates are changed from just secure to both secure and non-secure do anything to help this matter or am I looking at the wrong thing.

    I have tried removing IP addresses from DHCP in the hopes of resolving the conflicts, but still some seem to stick around and cause certain devices to not work until I can find the old device that was using the IP or simply set the non-functioning device to a static IP.

    Perhaps the solution is right under my nose, but I am not sure what I need to change in order to get this problem out of my way permanently.

    As always thanks for any light you can shed on my problem.
    It's not a war on drugs it's a war against personal freedoms!

  2. #2
    Senior Member mungyun's Avatar
    Join Date
    Apr 2004
    DNS is not what you are wanting. DNS is for resolving host names to IP addresses and wouldn't fix your problem with duplicate IP's. It is most likely a problem with your router. Do you have DHCP turned on for everything or are you statically assigning addresses to some of your devices? Sometimes when you do this, DHCP in your router(or server) might not notice that ip is taken and assign it to something else causing this conflict. If you are using static ip's for some things, set everything to DHCP and that should fix your problem.

    Hope this helps a little
    I believe in making the world safe for our children, but not our childrenís children, because I donít think children should be having sex. -- Jack Handey

  3. #3
    Senior Member Blunted One's Avatar
    Join Date
    Dec 2005
    The only router we have is the one connecting us to the internet. Everything else is on a lot of switches.

    If a device keeps trying to take an occupied address how can I have it re-request an different IP address? Or is that even possible.

    Everything except for a few machines, servers and consoles are on DHCP. The range of IP address is very large though so I don't get why the devices don't just grab the next availible IP. Any ideas?

    Thanks for the info.
    It's not a war on drugs it's a war against personal freedoms!

  4. #4
    THE Bastard Sys***** dinowuff's Avatar
    Join Date
    Jun 2003
    Third planet from the Sun
    A network card will always try to use the last ip address issued to it. In dhcp you can set detection conflict (ping first to see if the address is in use) in windows dchp its on the dhcp server name under properties and advanced.

  5. #5
    Senior Member
    Join Date
    Mar 2004
    I always follow the following plan when addressing a network

    .1-.10 = Network edge equipment
    .15-.40 = Servers
    .35-80 = Printers
    .100-200 = DHCP Scope for Workstations

  6. #6
    Senior Member WolfeTone's Avatar
    Join Date
    Jun 2007
    Another thing to consider is that you have only one DHCP Server on your network, if you have a Server make sure you use it's DHCP and turn off the DHCP on the Router.

  7. #7
    Senior Member Aardpsymon's Avatar
    Join Date
    Feb 2007
    St Annes (aaaa!)
    do you have enough addresses in your dhcp range? Check the expiry too, we've had the dhcp set not to expire. Found a device that was thrown away three years ago in the dhcp. eugh.
    If the world doesn't stop annoying me I will name my kids ";DROP DATABASE;" and get revenge.

  8. #8
    Senior Member Blunted One's Avatar
    Join Date
    Dec 2005
    This most recent duplicate IP was caused by two phones fighting over the same IP. I just had to track down the MAC address and tada found the issue reset that phone and it worked again.

    Damn VOIP...I liked it better when I plugged the damn phone into a wall and it worked...now these things have to load up before you can use them.
    It's not a war on drugs it's a war against personal freedoms!

  9. #9
    They call me the Hunted foxyloxley's Avatar
    Join Date
    Nov 2003
    3rd Rock from Sun
    what IP are tyou getting ?

    if it's the 169.254.x.x
    then you do't have DHCP enabled
    if it is a different set
    you might nee to set the DHCP scope correctly
    ie, only allow it to set IP's from x.x.x.20 - x.x.x.255, so you can allocate the first 20 to what you need or know

    my 2c
    55 - I'm fiftyfeckinfive and STILL no wiser,
    OLDER yes
    Beware of Geeks bearing GIF's
    come and waste the day :P at The Taz Zone

  10. #10
    Junior Member
    Join Date
    Jun 2005
    try setting the lease to a couple of hours...see if that makes a difference

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