Cian Davis wrote:
> Could there be, for some reason, a machine on the switch that has been
> spoofing the phantom MAC address? I know we were left scratching our
> heads a while ago when we forgot that we had spoofed MAC addresses on a
> machine (for totally legitimate reasons *cough*).
I am 100% sure this was caused by the server itself, not by proxy ARP,
crazy switches or other machines. When this server was rebooted the
problem went away - see my post from 22nd February for more details.
I have since figured out how the problem arose initially.
The were four IP addresses setup using sub interfaces:
We wanted to make eth0:0 go away.
The administrator (not me ;) commented out the entry for eth0:0 in
/etc/networking/interfaces, and ran /etc/init.d/networking restart.
It turns out this is actually the wrong thing to do, as ifdown -a only
removes the interfaces listed in /etc/networking/interfaces.
So eth0:0 was still up and running.
At this point the administrator edited /etc/networking/interfaces,
putting the configuration for eth0:1 into the stanza for eth0:0, and
putting the configuration for eth0:2 into the stanza for eth0:1. I'm not
sure if eth0:2 was commented out or not.
Then the administrator ran /etc/init.d/networking restart. Everything
looked fine - we now had the right IP addresses on the right interfaces.
Except - for some reason the kernel still thought it should answer ARP
requests for an IP address no longer configured on any of its interfaces
(The correct thing to do is to run ifconfig eth0:0 down and then edit
/etc/networking/interfaces to comment out the undesired sub interface.)
I'd love to try and reproduce this and submit the appropriate bug
reports but I haven't got the time right now :(
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