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Windows Thread, IP Conflict in Technical; Hi Have 600 PC's and 10 Servers.. I have a IP conflict with my main DC server 192.168.1.1 Now 192.168.1.1 ...
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    IP Conflict

    Hi

    Have 600 PC's and 10 Servers..

    I have a IP conflict with my main DC server 192.168.1.1

    Now 192.168.1.1 to 150 are reserved and the Server has the Static IP..

    Suddenly theyre is and IP Conflict..

    How to I find which PC has the conflicting IP Address as in the DHCP Leases it doesn't say

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    Geoff's Avatar
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    Re: IP Conflict

    Use wireshark and monitor the arp broadcasts. You should be able to determine the machines MAC address from this. Then consult your hardware inventory to determine the device that contains said network card.

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    Re: IP Conflict

    Wireshark http://www.wireshark.org/ ,if you don't have a full inventory of all of the MAC addresses you can at least narrow it down to a manufacturer as the first half of the MAC address will tell you the manufacturer http://www.coffer.com/mac_find/

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    Re: IP Conflict

    If you've got managed switches, you should be able to narrow down the swich the item is connected to by looking at the port address tables within the switchs once you know the MAC address.

    Mike.

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    Re: IP Conflict

    If you've got .1 to .150 reserved and its not in the DHCP lease, then you're probably looking for a pre-configured device which someone has connected - unless you've recently added any new print servers, switches or APs, your culprit is most likely someone's personal laptop.

    Typing tracert 192.168.1.1 into a DOS prompt should resolve the name for you, which might aid you in identifying what - and therefore where - it is.

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    Re: IP Conflict

    Yeah, just disconnect the server from the network

    cmd
    ping 192.168.1.?
    arp -a

    Now you've got the mac address.

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    Re: IP Conflict

    You have probably put a router or something like that on the network which has it's static IP defaulted to 192.168.1.1, either that or someone has plugged one into a network socket somewhere.

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    Re: IP Conflict

    Quote Originally Posted by j17sparky
    cmd
    ping 192.168.1.?
    arp -a

    Now you've got the mac address.
    That only works if you're connected to the same physical switch as the device in question, which he's obviously not.

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    Re: IP Conflict

    Quote Originally Posted by NickJones
    Quote Originally Posted by j17sparky
    cmd
    ping 192.168.1.?
    arp -a

    Now you've got the mac address.
    That only works if you're connected to the same physical switch as the device in question, which he's obviously not.
    Why would it matter?

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    Re: IP Conflict

    Try disconecting the server and accessing the IP address through a web browser. 192.168.1.1 is the default address for a number of pieces of hardware, most of which will have a web interface. Might give you a clue what your looking for.

    Steve

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    Re: IP Conflict

    Thanks Guys...... Working on it now....

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    Re: IP Conflict

    Quote Originally Posted by j17sparky
    Why would it matter?
    It matters because when I tried it here just now, I only saw devices on the same switch as me, so I don't see how it would help to track down the rogue device, as it could be anywhere on the network. I suppose you could go round every switch in turn, but that could be a lengthy process.

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    Re: IP Conflict

    Quote Originally Posted by NickJones
    Quote Originally Posted by j17sparky
    Why would it matter?
    It matters because when I tried it here just now, I only saw devices on the same switch as me, so I don't see how it would help to track down the rogue device, as it could be anywhere on the network. I suppose you could go round every switch in turn, but that could be a lengthy process.
    This should work so long as the system is on the same subnet as your station. If it is on a different subnet you will get the MAC address of the local router interface returned instead. This happens because MAC addresses are not routeable they are layer 2 only (OSI Model)

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    Re: IP Conflict

    I'm only saying what I found when I did it here - all I got were the devices on the same switch as me.

    If it were on a different subnet, it wouldn't be conflicting with the server, would it?

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    Re: IP Conflict

    all I got were the devices on the same switch as me.
    Not saying it didn't happen for some unknown reason, but responses limited to devices on the same switch is not normal. ARP should work for any device with a working TCP/IP stack on the same subnet.

    [Wrote a win32 ARP scanner eons ago (spits out MACs, vendors, DNS etc.) and that has always received the expected responses]



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