[CentOS] Networking just stopped working

[Chan Chung Hang Christopher]

Christopher Chan wrote:
> And now the thing is working again...

It's not working again.

Running tcpdump -i vlan seems to trigger something to get the network 
working again but as soon as I stop tcpdump...nada, zip, zilch.

Any ideas? I see no errors in the logs whether of the switch or the box, 
just about everything reports fine. Would the loading of the kernel 
bridge module cause this?