Learning OpenStack Networking - Third Edition

Flow rules for flat networks

Flat networks in Neutron are untagged networks, meaning there is no 802.1q VLAN tag associated with the network when it is created. Internally, however, Open vSwitch treats flat networks similarly to VLAN networks when programming the virtual switches. Flat networks are assigned a local VLAN ID in the Open vSwitch database just like a VLAN network, and instances in the same flat network connected to the same integration bridge are placed in the same local VLAN. However, there is a difference between VLAN and flat networks that can be observed in the flow rules that are created on the integration and provider bridges. Instead of mapping the local VLAN ID to a physical VLAN ID, and vice versa, as traffic traverses ...