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-rw-r--r-- | Documentation/faq/configuration.rst | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/Documentation/faq/configuration.rst b/Documentation/faq/configuration.rst index 4a98740c5..dc6c92446 100644 --- a/Documentation/faq/configuration.rst +++ b/Documentation/faq/configuration.rst @@ -281,3 +281,28 @@ the sense of OFPP_LOCAL) A: Open vSwitch does not support such a configuration. Bridges always have their local ports. + +Q: Why does OVS pick its default datapath ID the way it does? + + A: The default OpenFlow datapath ID for a bridge is the minimum + non-local MAC address among all of the ports in a bridge. This + means that a bridge with a given set of physical ports will always + have the same datapath ID. This is useful for virtualization + systems, which typically put a single physical port (or a single + bond of multiple ports) on a given bridge alongside the virtual + ports for running VMs. In such a setup, the IP address for the + NIC associated with a physical port gets migrated from the + physical NIC to the bridge port. The bridge port should have the + same MAC address as the physical NIC, so that the host doesn't + suddenly start using a different MAC, and taking the minimum MAC + address does this automatically and, if there is bond, + consistently. Virtual ports for running VMs do not affect the + situation because these normally have the "local" bit set, which + OVS ignores. + + If you want a stable MAC and datapath ID, you could set your own + MAC by ``hwaddr`` in ``other_config`` of bridge. + + :: + + ovs-vsctl set bridge br-int other_config:hwaddr=3a:4d:a7:05:2a:45 |