ML2

The Modular Layer 2 plug-in allows OpenStack Networking to simultaneously utilize the variety of layer 2 networking technologies found in complex real-world data centers. It currently includes drivers for the local, flat, VLAN, GRE and VXLAN network types and works with the existing Open vSwitch, Linux Bridge , and HyperV L2 agents. The ML2 plug-in can be extended through mechanism drivers, allowing multiple mechanisms to be used simultaneously. This section describes different ML2 plug-in and agent configurations with different type drivers and mechanism drivers.

Previously, Networking deployments were only able to use the plug-in that had been selected at implementation time. For example, a deployment running the Open vSwitch plug-in was only able to use Open vSwitch exclusively; it wasn't possible to simultaneously run another plug-in such as Linux Bridge. This was found to be a limitation in environments with heterogeneous requirements.

	Warning
	Disabling a ML2 type driver and re-enabling it later may lead to database inconsistencies if ML2 is reconfigured without support for that type.