In the case of a VLAN network type, we saw that the physical interface was separated in logical interfaces such as eth1.1002, eth1.1003, and so on. Moreover, each of these logical interfaces was placed on a Linux bridge corresponding to the OpenStack network.
In contrast, Flat Networks are created by placing the physical interfaces directly on the Linux bridge. This means that you can have only one Flat Network per physical interface on the compute node. Due to this reason, only the users with an administrative role are allowed to create a Flat Network.
In order to create a Flat Network and Subnet, you will need the following information, minimally:
The Network name
The Subnet name and IP address range
The physical network name—this information was configured in the ML2 plugin configuration file