[CentOS] Networking just stopped working

Thu Jul 8 05:41:13 UTC 2010
Christopher Chan <christopher.chan at bradbury.edu.hk>

On Thursday, July 08, 2010 01:32 PM, Kahlil Hodgson wrote:
> On 08/07/10 14:58, Christopher Chan wrote:
>>> If you have two machines on the same network with the same IP address
>>> you get behaviour like this.  Had this happen once when an engineer
>>> reset a UPSs and it took on the IP address of a main switch.
>>> arpwatch is your friend.
>> Unfortunately all addresses, both internal and Internet, on this box are
>> static and assigned so there is no hope of a collision. The dhcp server
>> does not serve any address in the same range that the box uses internally.
> I was referring to the case where another box (or network device) on the
> same network (i.e. plugged into the same switch/router/hub) has been
> given a static IP address the same as that used by the problem box.
> This could be a new server, a printer, a UPS, or any number of other
> network devices.  It could also be a device being reset to factory
> settings which conflicts with the problem box.

No new boxes. Not possible for any other box to be assigned the same ip 
internally via dhcp and definitely not the same Internet ip. Perhaps you 
care to explain why BOTH vlan interfaces stopped working? The odd chance 
that two other boxes each took one of the other ip address?

> I'm you have another Linux machine on the same network that is not
> having the same problem, try installing arpwatch.  It should pick up the
> conflict with 30mins or so.

The box with the problem just so happens to be the only box using 
bonding, 802.1q and a four port Qlogic Netxen NIC. I think the chances 
of there being a problem between these three more likely than some 
'ghost' boxes getting assigned the same ip addresses when I am the only 
admin around.