[CentOS] network intermitent, not sure if virtualization issue

Mon Feb 6 06:46:01 UTC 2012
Bob Hoffman <bob at bobhoffman.com>

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snip
centos 6 host, centos 6 virtual machine.
Network connection from outside server disappears in regards to the 
virtual server.


snip
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Tested the heck out of it.

Further testing shows the network unreachable, even if network restarted 
in host.
A simple ping from the virtual machine going out allows full traffic 
both ways.
Intermittent time out, it may last 5 minutes, it may last an hour, but 
it will disappear.


I found a small config sample on an old website in the middle of nowhere.
It had an addition to the /etc/sysconfig/network file of the host.
it added "GATEWAY=br0"

I did this and restarted the network service and I believe without me 
doing anything, this appeared in
the virtual machine message logs, something that had never appeared before.

kernel: Bridge firewalling registered

so hoping that is it...not sure if I would need to do that on the 
virtual machine or not.
I have been days at this. Literally rewrote every single ifcfg and conf 
file I could find.
Tried hundreds of permutations. Nothing has worked.

If this does not work I am willing to pay someone to end my week long 
battle with the virtual machine network being unreachable no matter what 
I do.
But only if you actually know this stuff and actually have experience 
with the virtual machine bridging..and hopefully have seen this type of 
issue...

<banging head on wall> <repeat> <rinse> <repeat>