An external network is a provider network that provides Neutron routers with external network access. Once a router has been configured and attached to the external network, the network becomes the source of floating IP addresses for instances and other network resources attached to the router. IP addresses in an external network are expected to be routable and reachable by clients on a corporate network or the internet. Multiple external provider networks can be segmented using VLANs and trunked to the same physical interface. Neutron is responsible for tagging the VLAN based on the network configuration provided by the administrator. Since external networks are utilized by VMs, they can be considered as part of the data plane.