Providing layer 2 connectivity to instances

Neutron and Nova work in tandem to configure networking on physical servers in the cloud. The LinuxBridge and Open vSwitch plugins provide both Neutron and Nova with the methods to provide connectivity to instances and other network resources.

Virtual network interfaces

By default, OpenStack leverages KVM, a kernel-based virtual machine, to provide a virtualization infrastructure to the Linux kernel that utilizes the hardware virtualization features of various processors.

When an instance is booted for the first time, a virtual network interface is created on the host that is referred to as a tap interface. The tap interface corresponds directly to a network interface within the guest instance. This action results in the host exposing the guest instance to the physical network.

In OpenStack, the name of the tap interface corresponds to the Neutron port UUID, or unique identifier, that the instance is plugged in to. The correlation of the tap interface...