Installation guide

Chapter 11. Network configuration

This chapter provides an introduction to the common networking configurations used by libvirt

based guest virtual machines. For additional information, consult the libvirt network architecture

documentation: http://libvirt.org/intro.html.

Red Hat Enterprise Linux 6 supports the following networking setups for virtualization:

virtual networks using Network Address Translation (NAT)

directly allocated physical devices using PCI device assignment

directly allocated virtual functions using PCIe SR-IOV

bridged networks

You must enable NAT, network bridging or directly assign a PCI device to allow external hosts

access to network services on guest virtual machines.

11.1. Net work Address T ranslat ion (NAT ) wit h libvirt

One of the most common methods for sharing network connections is to use Network Address

Translation (NAT) forwarding (also known as virtual networks).

Ho st co n f ig u rat io n

Every standard l i bvi rt installation provides NAT-based connectivity to virtual machines as the

default virtual network. Verify that it is available with the vi rsh net-l i st --al l command.

# virsh net-list --all

Name State Autostart

-----------------------------------------

default active yes

If it is missing, the example XML configuration file can be reloaded and activated:

# virsh net-define /usr/share/libvirt/networks/default.xml

The default network is defined from /usr/share/l i bvi rt/netwo rks/d efaul t. xml

Mark the default network to automatically start:

# virsh net-autostart default

Network default marked as autostarted

Start the default network:

# virsh net-start default

Network default started

Once the l i bvi rt default network is running, you will see an isolated bridge device. This device

does not have any physical interfaces added. The new device uses NAT and IP forwarding to connect

to the physical network. Do not add new interfaces.

⁠Chapt er 1 1 . Net work configurat ion