Visualizing traffic flow through Linux bridges
For an Ethernet frame to travel from a virtual machine instance to a device on the physical network, it will pass through three or four devices inside the host:
Network type | Interface type | Interface name |
all | tap | tapN |
all | bridge | brqXXXX |
vxlan | vxlan | vxlan-z (where Z is the VNI) |
vlan | vlan | ethX.Y (where X is the physical interface and Y is the VLAN ID) |
flat, vlan | physical | ethX (where X is the interface) |
To help conceptualize how Neutron uses Linux bridges, a few examples of Linux bridge architectures are provided in the following sections.
VLAN
Imagine an OpenStack cloud that consists of a single vlan provider network with the segmentation ID 100. Three instances have been connected to the network. As a result, the network architecture within the compute node resembles the following:
Figure 4.1
In Figure 4.1, three virtual machine instances are connected to a Linux bridge named brqXXXX via their respective tap interfaces. When the first instance was launched and connected...
