--- prelude: > The ML2 plug-in supports calculating the MTU for networks that are realized as flat or VLAN networks, by consulting the 'segment_mtu' option. Prior to Mitaka, 'segment_mtu' defaults to 0 which disables this feature. This creates slightly confusing API results when querying Neutron networks, since the plugins that support the MTU API extension would return networks with the MTU equal to zero. Networks with an MTU of zero make little sense, since nothing could ever be transmitted. In Mitaka, 'segment_mtu' now defaults to 1500 which is the standard MTU for Ethernet networks in order to improve the "out of box" experience for typical deployments. features: - In Mitaka, queries to the Networking API for network objects will now return network objects that contain a sane MTU value. upgrade: - Operators using the ML2 plug-in with existing data may need to perform a database migration to update the MTU for existing networks