All Cisco-Network Study Notes: Types of routers in an MPLS network

C Router: A C, or Customer Internal Router, is a router that is purely internal to a customer's network. The C router connects to other C routers and to the CE router. It does not connect directly to any P or PE routers. This router does not run MPLS.
CE Router: A CE, or Customer Edge Router, is the connection point between the customer's network and the MPLS network. The CE router talks to PE routers and C routers, but not to the P routers. This router also does not run MPLS.
PE Router: The PE, or Provider Edge Router, is where much of actual work takes place. These routers run MPLS and are part of the carrier's MPLS network, but they also communicate with the customer's CE router and may take part in the customer's routing protocol. PE routers are the end points of the VPNs.
P Router: P, or Provider Internal Routers, are purely internal to the carrier's MPLS network. This router runs MPLS to communicate with the rest of the carrier's network and transport customer packets through VPNs. However, the P router does not see the customer routing tables or VRF information. These are the backbone of the MPLS network, and they talk to PE routers and other P routers.