Strange network thing

[Lonni J Friedman]

On Thu, Mar 6, 2008 at 4:10 PM, Stuart Biggerstaff
<biggers at lindahall.org> wrote:
> 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?

Are the IP addresses static or DHCP?  Prior to trying to bring up the
NIC (and getting the error), what happens if you attempt to ping the
IP address?

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
L. Friedman                                    netllama at gmail.com
LlamaLand                       https://netllama.linux-sxs.org