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Old 03-09-2008, 09:37 PM   #1
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Smile How to check and solve IP Address conflict.

Hi, in my LAN there have around 20pcs linux and window XP system. There have 3 PC having a same IP Address,so IP Address conflict. How to check is it inside the LAN have any system(PC) having IP Address conflict,what command should be use arp or what? than can find the all IP Address conflict PC's MAC address.

Thank you.
Old 03-10-2008, 04:23 AM   #2
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if you switch them to get their address by dhcp you'll be better off probably
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Old 03-11-2008, 12:04 AM   #3
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you may try:

# arping -I <interface> <ip_addr>

When this command is issued it sends arp probes trough the network interface of your choice for the specified ip address. If two or more NIC reply to your request, they are in conflict.
Old 03-18-2008, 12:44 PM   #4
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I pasted your code & this is what I got:
# arping -I ethN
arping: invalid option -- I
ARPing 2.01, by Thomas Habets <>
usage: arping [ -0aAbdFpqrRv ] [ -w <us> ] [ -S <host/ip> ] [ -T <host/ip ]
              [ -s <MAC> ] [ -t <MAC> ] [ -c <count> ] [ -i <interface> ]
              <host/ip/MAC | -B>
Are we using different vers. of arping, or did you forget to proofread your post? (Can happen to anyone.)
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Old 03-21-2008, 12:45 AM   #5
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Yeah man, we got totally different versions of arping. Mine was written by another guy. It is shipped by default with slackware linux.
Old 03-21-2008, 04:47 AM   #6
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system administration

If there are only 20 PC's involved, then I would suggest to assign proper and unique IP's to all of them and file the IP numbers in a proper system admin documentation (very handy sometimes).

If you don't want to deal with IP numbers and there is no reason to have fixed numbers, then you should really switch to DHCP, as already suggested. Even internal web, samba and other servers will work fine with DHCP, because they usually run forever, so their IP is not changed by the Router.

Hope this helps,

Fedora Development

Last edited by simplicissimus; 04-02-2008 at 05:50 AM.
Old 03-21-2008, 12:44 PM   #7
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Using DHCP you can setup static leases on the router, so that you can refer to the machines by hostname (/etc/hosts) or IP address.

Its sounds like the LAN is a mess that needs to be fixed.
Old 03-22-2008, 03:17 AM   #8
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For 20 IP addresses, it would be easy to keep track of them all in a spreadsheet. If you use Open Office Calc, a format for a column like "192.168.1."# and then filling down a range of numbers (the last octat) can be convenient. Then if someone needed another IP address, it would be a simple matter of opening the spreadsheet to find an available IP address. If you have some hosts that use DHCP and some servers on fixed IP addresses, make sure that you assign the fixed addresses outside the range of IP's that the DHCP server serves up. If you run a DHCP server on a computer, you can configure it to give fixed addresses to certain hosts based on their MAC addresses.

Last edited by jschiwal; 03-22-2008 at 05:40 AM.


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