Find IP or hostname based on MAC address

How can you find a computer's IP or name on the LAN using only a MAC address?
garryshapeAsked:
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dfxdeimosCommented:
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garryshapeAuthor Commented:
There's an IP conflict on my computer and it's only giving me the MAC address of the other system, not their name or IP.
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dathhoCommented:
parse the arp table...
arp -a > findstr 00-1a-a2-a4-59-82
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dathhoCommented:
Well, the conflict is with the address you are trying to use, No?
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garryshapeAuthor Commented:
Well it says:

The system detected an address conflict for IP address 10.1.20.159 with the system having network hardware address 00:0F:1F:C9:0F:34. Network operations on this system may be disrupted as a result
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dfxdeimosCommented:
Yeah, you could just switch your IP address and then ping your old one to resolve the name. Or look in your DNS console and see if the new PC dynamically registered it's name in DNS.
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garryshapeAuthor Commented:
C:\>arp -a > findstr 00:0F:1F:C9:0F:34
ARP: bad argument: 00:0F:1F:C9:0F:34
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dathhoCommented:
You need to use the dashs.  This is the way it's represented in the table. Or just look at the whole table (arp -a)
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garryshapeAuthor Commented:
I did it from another PC (My PC) and I didn't see that event ID mac address in the table.

Would running the ARP -a from the PC the conflict occured on show anything different you think?
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garryshapeAuthor Commented:
ran the ARP -a on the PC that got disconnected due to a conflict, but nothing showed up in the table other than the PC network mac address  itself.
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dathhoCommented:
Not sure.  Give it a try.  If you have a DHCP server and the address came was dynamically configured you can get more info there.  You really want to find this confilcting node, right?
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Fred MarshallPrincipalCommented:
From a computer that is on the network, open the Command Line and type this:

arp -a <enter>

The resulting report should list all IP addresses along with MAC addresses.  
Just match up the MAC address in this report and you have the IP address.
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dfxdeimosCommented:
Just change your IP address to a known free one. Ping your OLD address. The ping will give you the hostname. Beat said hostname with a brick until it releases your IP address...

Book it. Done.
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sachiorossCommented:
If you're still having trouble, try pinging the broadcast address for the subnet.  Depending on how you have this set it, this might be as simple as pinging "192.168.1.255."  Tip: if you can, use ipconfig/all and take a quick look at the subnet mask.

If it's: 255.255.255.0 then ping (your IP # "192").(Your IP # "168").(Your IP # "1").255.

If it's: 255.255.0.0 then ping x.x.255.255

After that, then run arp -a and you should see all computers on the network that are currently connected.  I believe this should work even with an address conflict.

Note: pinging the broadcast address might result in nothing coming back (i.e. "request timed out").  Don't worry, it may have still worked.  If the amount of listings in your arp table changed then it did work.

Goodluck.

{
>ping 192.168.1.255
>...
>Request Time Out
>arp -a
>[arp table listings]
}
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sachiorossCommented:
Oh, and after that: try using nslookup [desired ip address] and you should also be able to resolve the hostname.
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garryshapeAuthor Commented:
Thanks for the help, but unfortunately I can't try this until later since I am no longer at the network. I will let you know my results by tomorrow or Monday.
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MikeKaneCommented:
If you have a cisco switch in use at your location, you can run a command from the switch such as :

show mac address-table | incl 000F:1FC9:0F34  

That should give you either the port its connected to, or the uplink.   If its the uplink, you run the same command form the uplink'ed switch and check for the same result  (btw you check for uplink with    SHOW CDP NEI )

Once you have the port on the switch, you can trace the cable back to the desk of the offending system.  

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