Virtual networking

Many people consider virtual networking in libvirt to be complicated. Perhaps it is the number of options available to provide networking to a virtual machine that makes the libvirt networking appear complicated.

The main component of libvirt networking is the virtual network switch, also known as the bridge. You can imagine a bridge as a physical switch. In a real switch, there are a limited number of physical ports to attach to your servers. Here, on the Linux bridge, there are unlimited numbers of virtual ports to which the interfaces to virtual machines are attached. Similar to a physical switch, bridge learns the MAC addresses from the packets it receives and stores those MAC addresses in the MAC table. The packet (frames) forwarding decisions are taken based on the MAC addresses that it learned and stored in the MAC table.

We mentioned about the interfaces attached to the ports of a bridge. These interfaces are special network devices called TAP devices. If you try...