•Provider (P) network—P network is the backbone under the control of the enterprise IT.
•Provider edge (PE) interface—The PE interface is located at the edge of a provider network and faces the customer.
•Provider edge (PE) router—A router belonging to a provider with one or more PE interfaces; also known as an edge label switching router (ELSR). PE routers connect to VPN site routers to provide connectivity into an MPLS network.
•Provider (P) router—A router belonging to a provider with no PE interfaces. P routers reside in the core of the service provider and provide interconnectivity to PE routers.
•Customer edge (CE) interface—An interface on a customer router that points towards a provider, where customer router means a router that is logically part of the customer network no matter where it is physically located or who manages it.
•Customer edge (CE) router—A router with at least one customer edge interface that resides on a customer premise. In a typical campus design, access layer switches are Layer 2-attached to the distribution layer. Access layer VLANs terminate on the first Layer 3 device (the distribution layer), so CE router terminology does not apply to campus networks. Consider the CE box as a Layer 2 switch connected to the distribution layer router.
•Multi-VRF (CE) router—This router supports VRFs but not full MP-BGP VPNs. This could reside on a customer premise. In a campus network, this could be any Layer 3 switch where VLANs terminate.