On recent fedora-18 NetworkManager started to set default STP for the bridges
to on, this is a change in the default of distribution, which up until now was
off, I opened a bug.
If you experiencing disconnect of hosts from network due to STP detection, a
workaround is available.
To the wired interfaces (eth0, em1...) before host deployment, this will be
copied to the management bridge and will prevent NetworkManager to use its
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