The LabelEdgeRouter (LER) is one of the two most important network components in an MPLS, Multi-Protocol Label Switching (MPLS) network. It is deployed at the edge of an MPLS domain and is typically part of an edge router( ER), such as a CE router, Customer Edge.
The label edge router is the only MPLS node with full routing functionality; it provides the datagrams with labels and thus allocates the routing information to the datagrams for subsequent forwarding into the MPLS domain. Forwarding via the specified routes, i.e., the label switched paths( LSP), is performed with defined service classes.
The LER router simultaneously serves as a generation and termination point in a Label Switched Path (LSP).