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Weird IP Address and MAC conflict on AD 2003 R2 network

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  • Weird IP Address and MAC conflict on AD 2003 R2 network

    Hi all. Your help is most appreciated.

    I have a user on my network that requires static IP for elevated Internet access through our Cisco ASA5100. He had a Dell laptop originally, and now has a newer Lenovo PC. I reused the IP of course without issue and reused the laptop by re-imaging and using it occassionally for testing and letting it get a DHCP served IP.

    The issue now is the user with the new Lenovo is getting Event ID 4199 errors based on the MAC of the old laptop when I on occasion plug it into the network, even though it is not using the same static IP. I have tried arp- a on both laptop and PC and saw no conflicts. I made sure the static IP is not within the DHCP scopes allowed for dynamic access. I checked the DC and the DHCP servers for any issues, but nothing.

    Unsure as to where to go from here. We are using Windows 2003 R2 AD with DHCP enabled for most users, Cisco switches, Windows XP SP2 and SP3. I could keep the laptop off the network, but some insight as to what may be causing this would be helpful.

    Thx

    Davige

  • #2
    Re: Weird IP Address and MAC conflict on AD 2003 R2 network

    Clear the Arp Cache.

    "netsh interface ip delete arpcache"

    run this on machines in question and possibly the dhcp server.

    you can also clear arp cache on your swithes if all else fails.
    MCSE 2003; MCTS Vista; Sec+; CCNA
    Attitude Makes The Difference!
    in other words you got to WANT to do it..

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    • #3
      Re: Weird IP Address and MAC conflict on AD 2003 R2 network

      To Ikon: thx for your post. I tried to clear the arp on both laptop and PC, the DHCP server and the switches, and still the same thing. Now the laptop does not even connect on boot up to the network! Have no idead what to do now.

      Davige

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      • #4
        Re: Weird IP Address and MAC conflict on AD 2003 R2 network

        Originally posted by ikon View Post
        Clear the Arp Cache.

        "netsh interface ip delete arpcache"

        run this on machines in question and possibly the dhcp server.

        you can also clear arp cache on your swithes if all else fails.
        Or just type ARP -A * in CMD
        use ARP -A to view arp table and ARP -A > ARP.TXT to send the table to txt file

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