13 Managing Networks #
This chapter introduces common networking configurations supported by libvirt . It does not depend on the hypervisor used. It is valid for all hypervisors supported by libvirt , such as KVM or Xen. These setups can be achieved using both the graphical interface of Virtual Machine Manager and the command line tool virsh .
There are two common network setups to provide a VM Guest with a network connection:
- A virtual network for the guest
- A network bridge over a host’s physical network interface that the guest can use
13.1 Virtual Networks #
A virtual network is a computer network which does not consist of a physical network link, but rather uses a virtual network link. Each host can have several virtual networks defined. Virtual networks are based on virtual devices that connect virtual machines inside a hypervisor. They allow outgoing traffic translated to the LAN and are provided with DHCP and DNS services. Virtual networks can be either isolated , or forwarded to a physical network.
Guests inside an isolated virtual network can communicate with each other, but cannot communicate with guests outside the virtual network. Also, guests not belonging to the isolated virtual network cannot communicate with guests inside.
On the other hand, guests inside a forwarded (NAT, network address translation) virtual network can make any outgoing network connection they request. Incoming connections are allowed from VM Host Server, and from other guests connected to the same virtual network. All other incoming connections are blocked by iptables rules.
A standard libvirt installation on SUSE Linux Enterprise Server already comes with a predefined virtual network providing DHCP server and network address translation (NAT) named «default».
13.1.1 Managing Virtual Networks with Virtual Machine Manager #
You can define, configure, and operate both isolated and forwarded virtual networks with Virtual Machine Manager.
13.1.1.1 Defining Virtual Networks #
- Start Virtual Machine Manager. In the list of available connections, right-click the name of the connection for which you need to configure the virtual network, and then select Details .
- In the Connection Details window, click the Virtual Networks tab. You can see the list of all virtual networks available for the current connection. On the right, there are details of the selected virtual network.