Strange network thing

[Stuart Biggerstaff]

We just moved a server from our internal network to our DMZ, and
assigned it an appropriate new fixed IP.  Now, when eth0 tries to start,
it shows the message "Error, some other host already uses address
xxx.xxx.xxx.xxx," and the interface refuses to start.

We can start it on a separate switch and physically move the cable back,
and it works, and other hosts in the subnet can ping it but show nothing
live at that IP when it's down.  To me that says there really isn't
another host with the IP, but the problem is still external, or I'd have
it on the dummy network.

I've had an issue with boxes with two NICs suddenly swapping them when
upgrading the OS or even occasionally on kernel updates, so I disabled
the second NIC in the configuration, and apparently caused it to do it
preemptively.  So just after moving it, we ended up using a different
MAC address, and apparently something in the network infrastructure has
the association between that address and the IP cached, and isn't
letting it go.  My first guesses would be the local switch and the
firewall appliance, but I've confirmed both to show the current
configuration.

Anyone have a suggestion on how to determine where the erroneous
configuration is cached, and maybe how I can clear it?


Stuart Biggerstaff
Systems Technician
Linda Hall Library of Science Engineering & Technology
5109 Cherry St.
Kansas City, Missouri 64110-2498

Phone:	(816) 926-8748
	(800) 662-1545 x748
FAX:	(816) 926-8790
URL:	www.lindahall.org