I've got a good one.
Last week, my manager called me up and told me that there's an IP address conflict on our network, and that the network ninjas traced it to the HQ building, floor 7 LAN closet (which terminates the cabling for floors 6, 7 and 8). The problem arose when one of our travelling laptop users brought their laptop back into the HQ and tried to use it. The Windows95-based ThinkPad squealed, saying it had a conflict with IP address xxx.xxx.xxx.xxx (it's definitely in our block), with the MAC address of 00:00:81:24:B0:B8.
I looked up ( the OUI (000081) from the MAC and discovered that 'twas a Bay Networks device. Great! Off I went, looking for a Baystack hub or something ... until much later, after I'd looked at every goddamned Bay Networks hub in the HQ complex, and I hadn't matched the MAC to the supposedly erring device. Fsck!
To this day, we still don't know what the device was. The network ninjas did some of their funky oriental magic and removed the IP address from DHCP, then we allowed the laptop to boot and acquire another IP address. That fixed the problem, but it could happen again.
How would you have found the conflicting device?
Last week, my manager called me up and told me that there's an IP address conflict on our network, and that the network ninjas traced it to the HQ building, floor 7 LAN closet (which terminates the cabling for floors 6, 7 and 8). The problem arose when one of our travelling laptop users brought their laptop back into the HQ and tried to use it. The Windows95-based ThinkPad squealed, saying it had a conflict with IP address xxx.xxx.xxx.xxx (it's definitely in our block), with the MAC address of 00:00:81:24:B0:B8.
I looked up ( the OUI (000081) from the MAC and discovered that 'twas a Bay Networks device. Great! Off I went, looking for a Baystack hub or something ... until much later, after I'd looked at every goddamned Bay Networks hub in the HQ complex, and I hadn't matched the MAC to the supposedly erring device. Fsck!
To this day, we still don't know what the device was. The network ninjas did some of their funky oriental magic and removed the IP address from DHCP, then we allowed the laptop to boot and acquire another IP address. That fixed the problem, but it could happen again.
How would you have found the conflicting device?