IP conflicts, details inside
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Thread: IP conflicts, details inside

  1. #1
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    IP conflicts, details inside

    Ok, my boss is running an IBM Lenovo laptop on a docking station. He wants wireless and the ethernet cord in and active. He gets an ip conflict everythime he connects. He had a dhcp reservation for both his wireless IP and wired IP. I have since removed the reservation on the wireless as it wasnt needed.
    We are running WINS and DHCP and DNS due to the cobbeled state of our network. His Netbios name was attached to 2 different IP's, which is what i thought was cuasing the conflict. I have tried to mimick my settings tohis, as I do not get a conflict, but to no avail.
    I can't find much on setting WINS for a mixed network, and I really don't have a ton of experience with all of this being 6 weeks on the job and fresh out of college. His ip's in a ipconfig /all reveal two seperate ip's. When I run ntbstat -a i get two ip's, but both are associated to his Wireless Mac address. Also in ipconfig /all his wireless shows up first then his ehternet nic (which is different from al other machines here, but i cant find anything about it or I am search the wrong key words)
    Can anyone point me in a direction? I am trying to install a wireless controller and AP's (which I know nothing about of course, but more than the vendor) and also configuring Groupwise 6.5, so him bothering me with an Ip conflict is killing me.
    Thanks

  2. #2
    AO übergeek phishphreek's Avatar
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    An ip conflict means that more than one machine (or nic) has the same ip address.

    You say you are using DHCP. It sounds like either the DHCP server assigned one ip addresses to two different NICs (different mac addresses) or the DHCP server assigned it to one NIC and another user statically assigned the same ip address to their NIC.

    If it were me, I'd make note of the ip addresses being used on the machine reporting the conflict.
    (BTW: did you statically assign these addresses? or were they assigned via DHCP?)

    Then take that machine offline and go to another machine on your network and try to ping it or resolve the other host. Then you can find out if that machine was statically assigned and change it back to DHCP.

    The DHCP server *should not* have assigned one ip address to two different mac addresses. You can check the DHCP server to see who the lease belongs to.

    Also, if you did assign one of them statically... that is ok, as long as it is outside of the DHCP scope.

    Meaning, if you're DHCP server assigns addresses in the 192.168.0.2-50 range, don't statically assign one of those addresses. Use 51-254. etc.
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  3. #3
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    The guy before me set up DHCP reservations. I will have to look more closely, but in my active ip's list from the DHCP server i just see the ip once. I'll muddle through it, so maybe I can move on to other things.....thanks!

  4. #4
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    His netbios name in WINS shows it as a workstation with an IP address and then as a fileserver with his wireless ip address. Is this the conflict? But this seems to be the case for 2 other laptops if i enable wireless while they are plugged in. All 3 laptops have DHCP reservations on the ethernet NIC, but not the wireless ip's

  5. #5
    AO übergeek phishphreek's Avatar
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    No, you should only have an ip conflict if two nics are assigned the same ip on the same subnet.

    One machine have many names or aliases in dns or whatever.
    Those are just means to find the machine.

    First thing I would do is mark down the IP(s) that the machine is using.

    Then remove it from the network (both wired and wireless).

    Try to ping those addresses to see if they respond.

    If they respond, then there is another machine with the same ip address and thats why you see the conflict. Go to that machine and see if it is statically assigned. If so, then change it to DHCP.

    Is it possible that the former admin assumed that the person with the laptop would be using one or the other (wired or wireless) and forced the same ip to both NICs?

    BTW: Why do they need both wireless and wired at the same time?
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  6. #6
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    Because he is my boss.......
    honestly, I have reading so much on VLANS and Meru's wireless mesh system to get it up and running before we get busy, and setting up Active Directory, this ip conflict just pisses me off. I have no clue why he wants them both on at the same time. I asked that around the same time I got my head chewed off for mentioning we needed IDS in our network. He yelled and yelled and said we were secure. The following week i brought 7 2003 servers up to Service Pack 1. So, I have a chip on my shoulder at this point with how he goes about things.
    And any time I do anything I need to explain it to him like a 2 year old so he can "learn" as he says.
    Is there a command line command I can issue to list ip's? Because the current leases i see in DHCP show his ip's once only. But it may be more to it than that.
    Thanks

    fruastrate junior entry level sys admin <sr sys admin is on vacation>

    kill me now please!

  7. #7
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    An arp -a 10.10.xx.xxx reveals just one Mac

    nbtstat -a 10.10.xx.xxx reveals something unique to his system two (00) listings and one <1e>


    Name Type Status
    ---------------------------------------------
    MCLENOVO <00> UNIQUE Registered
    ADMIN <00> GROUP Registered
    ADMIN <1E> GROUP Registered

  8. #8
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    netbios-ns (137/tcp)


    Synopsis :

    It is possible to obtain the network name of the remote host.



    Description :

    The remote host listens on udp port 137 and replies to NetBIOS
    nbtscan requests.
    By sending a wildcard request it is possible to obtain the name of
    the remote system and the name of its domain.



    Risk Factor :

    None



    Plugin output :

    The following 3 NetBIOS names have been gathered :

    MCLENOVO = Computer name
    ADMIN = Workgroup / Domain name
    ADMIN = Browser Service Elections

    The remote host has the following MAC address on its adapter :
    00:
    CVE : CVE-1999-0621
    Plugin ID : 10150

  9. #9
    AO übergeek phishphreek's Avatar
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    I don't know why you keep messing with netbios/wins/dns. This is an IP problem...

    Again, there are two nics with the same ip address. You need to find which two NICs.
    Or, simply find an unused IP address outside of the DHCP scop and assign this laptop a new ip.
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  10. #10
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    I turn the laptop off. The ipis not able to be pinged. turn it on, the laptop tells me there is an ip conflict. No event manager record. Etherreal doesnt show 2 dupes of the NIC. WINS Seemed to be what might be giving me the conflict

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