USB NIC adaptor strange behavior

[Derek Broughton]

Michael J. Lynch wrote:

> Derek Broughton wrote:
>> Michael J. Lynch wrote:
>> 
>> 
>>>I have a system that has an onboard NIC and a USB NIC and both
>>>work as expected with one exception.  When I run ifconfig it shows
>>>the onboard NIC as eth0 and the USB NIC as eth1.  If I disconnect
>>>the USB NIC by unplugging it from the USB bus I loose all network
>>>connectivity to the box.  If I run ifconfig, it shows *eth0* (the
>>>onboard NIC) down and *eth1* (the USB NIC) still up and configured
>>>even though it was the one disconnected.  Anyone have any ideas
>>>where I should start looking for the problem.  I'm not real familiar
>>>with hotplug so I'm not sure where to start looking.
>>>
>> 
>> How can you tell that eth1 was the USB NIC ?  I have to admit I can't
>> imagine how an onboard NIC could get recognized _after_ the USB, but it
>> sure looks that way.
> 
> Ok...I dunno what changed but it seems to be working ok now.  However,
> my syslog.0 file does in fact show that the USB NIC was assigned to
> eth0 rather than eth1.  But, as I stated, current syslogs show that it
> is being assigned to eth1.  FM!!  Maybe just a fluke...dunno...ain't
> gonna worry about it for now.

OK, then there's a number of things you can do.  

You can make sure you never boot with the USB NIC connected.

You can play with udev (theoretically - I've never tried renaming
interfaces, but I'm pretty sure it's possible) or ifrename to make sure
that the USB interface always has a name other than eth* - then it can't
collide.

You might blacklist a module in /etc/hotplug/blacklist - but I don't have a
clue how you'd figure out which one - or force load a module
in /etc/modules.

I'd be really surprised if this never happens again!
-- 
derek