Re: How to tell kernel to not bring up a network interface

Rich,

Run lspci and find out what the ethernet controller is on both the Dell 
and the Sony. It could be the driver cannot detect link state 
information on the Sony, so when the network cable is unplugged the 
interface is still reported as UP.

Run netplugd -F -c /dev/null

This will run netplugd in the foreground without a config file, so 
ruling out any config problems. Plug in and unplug the ethernet cable 
and see if there is any change in the output. If netplugd doesn't see 
any change, you know its a driver issue. If there is a change, its a 
config issue.

If there is a driver issue, you may need to run lspci -v to get verbose 
information. Note this down and report it to the bug tracking system at 
kernel.org with all the evidence about the link state failure. Include 
the output of uname -a so they can see what kernel you are using as well 
as what platform it was built for.

You never know, the next kernel release may have a patch for your 
problem in it.

https://bugzilla.kernel.org/

Best,

John