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This is a very important section, please make sure you read this thoroughly. This section details how to configure bridges using the native implementation in Linux. Please refer to the next section if you intend to use OpenVswitch 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: We now have to configure the three VLAN interfaces: vi /etc/sysconfig/network-scripts/ifcfg-eth0.100 vi /etc/sysconfig/network-scripts/ifcfg-eth0.200 vi /etc/sysconfig/network-scripts/ifcfg-eth0.300 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 We do the same for cloudbr1 vi /etc/sysconfig/network-scripts/ifcfg-cloudbr1 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: 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!