Network Types The OpenStack Networking configuration provided by the Rackspace Private Cloud cookbooks allows you to choose between VLAN or GRE isolated networks, both provider- and tenant-specific. From the provider side, an administrator can also create a flat network. The type of network that is used for private tenant networks is determined by the network_type attribute, which can be edited in the Chef override_attributes. This attribute sets both the default provider network type and the only type of network that tenants are able to create. Administrators can always create flat and VLAN networks. GRE networks of any type require the network_type to be set to gre. Namespaces For each network you create, the Network node (or Controller node, if combined) will have a unique network namespace (netns) created by the DHCP and Metadata agents. The netns hosts an interface and IP addresses for dnsmasq and the quantum-ns-metadata-proxy. You can view the namespaces with the ip netns [list], and can interact with the namespaces with the ip netns exec <namespace> <command> command. Metadata Not all networks or VMs need metadata access. Rackspace recommends that you use metadata if you are using a single network. If you need metadata, you may also need a default route. (If you don't need a default route, no-gateway will do.) To communicate with the metadata IP address inside the namespace, instances need a route for the metadata network that points to the dnsmasq IP address on the same namespaced interface. OpenStack Networking only injects a route when you do not specify a gateway-ip in the subnet. If you need to use a default route and provide instances with access to the metadata route, create the subnet without specifying a gateway IP and with a static route from 0.0.0.0/0 to your gateway IP address. Adjust the DHCP allocation pool so that it will not assign the gateway IP. With this configuration, dnsmasq will pass both routes to instances. This way, metadata will be routed correctly without any changes on the external gateway. OVS Bridges An OVS bridge for provider traffic is created and configured on the nodes where single-network-node and single-compute are applied. Bridges are created, but physical interfaces are not added. An OVS bridge is not created on a Controller-only node. When creating networks, you can specify the type and properties, such as Flat vs. VLAN, Shared vs. Tenant, or Provider vs. Overlay. These properties identify and determine the behavior and resources of instances attached to the network. The cookbooks will create bridges for the configuration that you specify, although they do not add physical interfaces to provider bridges. For example, if you specify a network type of GRE, a br-tun tunnel bridge will be created to handle overlay traffic.