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This is a very important section, please make sure you read this thoroughly. In order to forward traffic to your instances you will need at least two bridges: public and private. By default these bridges are called cloudbr0 and cloudbr1, but you do have to make sure they are available on each hypervisor. The most important factor is that you keep the configuration consistent on all your hypervisors.

There are many ways to configure your network. In the Basic networking mode you should have two (V)LAN's, one for your private network and one for the public network. We assume that the hypervisor has one NIC (eth0) with three tagged VLAN's: VLAN 100 for management of the hypervisor VLAN 200 for public network of the instances (cloudbr0) VLAN 300 for private network of the instances (cloudbr1) On VLAN 100 we give the Hypervisor the IP-Address 192.168.42.11/24 with the gateway 192.168.42.1 The Hypervisor and Management server don't have to be in the same subnet!

It depends on the distribution you are using how to configure these, below you'll find examples for RHEL/CentOS and Ubuntu. The goal is to have two bridges called 'cloudbr0' and 'cloudbr1' after this section. This should be used as a guideline only. The exact configuration will depend on your network layout.

The required packages were installed when libvirt was installed, we can proceed to configuring the network. First we configure eth0 vi /etc/sysconfig/network-scripts/ifcfg-eth0 Make sure it looks similair to: DEVICE=eth0 HWADDR=00:04:xx:xx:xx:xx ONBOOT=yes HOTPLUG=no BOOTPROTO=none TYPE=Ethernet We now have to configure the three VLAN interfaces: vi /etc/sysconfig/network-scripts/ifcfg-eth0.100 DEVICE=eth0.100 HWADDR=00:04:xx:xx:xx:xx ONBOOT=yes HOTPLUG=no BOOTPROTO=none TYPE=Ethernet VLAN=yes IPADDR=192.168.42.11 GATEWAY=192.168.42.1 NETMASK=255.255.255.0 vi /etc/sysconfig/network-scripts/ifcfg-eth0.200 DEVICE=eth0.200 HWADDR=00:04:xx:xx:xx:xx ONBOOT=yes HOTPLUG=no BOOTPROTO=none TYPE=Ethernet VLAN=yes BRIDGE=cloudbr0 vi /etc/sysconfig/network-scripts/ifcfg-eth0.300 DEVICE=eth0.300 HWADDR=00:04:xx:xx:xx:xx ONBOOT=yes HOTPLUG=no BOOTPROTO=none TYPE=Ethernet VLAN=yes BRIDGE=cloudbr1 Now we have the VLAN interfaces configured we can add the bridges on top of them. vi /etc/sysconfig/network-scripts/ifcfg-cloudbr0 Now we just configure it is a plain bridge without an IP-Adress DEVICE=cloudbr0 TYPE=Bridge ONBOOT=yes BOOTPROTO=none IPV6INIT=no IPV6_AUTOCONF=no DELAY=5 STP=yes We do the same for cloudbr1 vi /etc/sysconfig/network-scripts/ifcfg-cloudbr1 DEVICE=cloudbr1 TYPE=Bridge ONBOOT=yes BOOTPROTO=none IPV6INIT=no IPV6_AUTOCONF=no DELAY=5 STP=yes With this configuration you should be able to restart the network, although a reboot is recommended to see if everything works properly. Make sure you have an alternative way like IPMI or ILO to reach the machine in case you made a configuration error and the network stops functioning!

All the required packages were installed when you installed libvirt, so we only have to configure the network. vi /etc/network/interfaces Modify the interfaces file to look like this: auto lo iface lo inet loopback # The primary network interface auto eth0.100 iface eth0.100 inet static address 192.168.42.11 netmask 255.255.255.240 gateway 192.168.42.1 dns-nameservers 8.8.8.8 8.8.4.4 dns-domain lab.example.org # Public network auto cloudbr0 iface cloudbr0 inet manual bridge_ports eth0.200 bridge_fd 5 bridge_stp off bridge_maxwait 1 # Private network auto cloudbr1 iface cloudbr1 inet manual bridge_ports eth0.300 bridge_fd 5 bridge_stp off bridge_maxwait 1 With this configuration you should be able to restart the network, although a reboot is recommended to see if everything works properly. Make sure you have an alternative way like IPMI or ILO to reach the machine in case you made a configuration error and the network stops functioning!