** Impact **

Since Essex, all instances will have an eth0 MAC address in the range
of FA:16:3E, which is near the end of the MAC address space.

 When openvpn is started, a TAP interface is created with a random
generated MAC address. Chances are high the generated MAC address is
lower in value than the eth0 MAC address. Once the tap interface is
added to the bridge interface, the bridge interface will no longer have
the eth0 MAC address, but take over the TAP MAC address. This is a
feature of the linux kernel, whereby a bridge interface will take the
MAC address with the lowest value amongst its interfaces. After the ARP
entries expire, this will result in the cloudpipe instance being no
longer reachable.

This fix, randomly generates a MAC address starting with FA:17:3E, which
is greater than FA, and will thus ensure the brige will keep the eth0
MAC address.

** Development Fix **

This fix has been addressed in https://review.openstack.org/6327 and
already fixed in quantal.

** Stable Fix **

This fix has been addresses in the stable/essex tree in
https://review.openstack.org/6327

** Regression Potential **

Minimal, it is a hardyly used feature in Openstack on Ubuntu.

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https://bugs.launchpad.net/bugs/975043

Title:
  [SRU] Cloudpipe VPN instance can loose connectivity after starting
  openvpn

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