What type of router at the edge of an MPLS network allows traffic onto a Label Switched Path (LSP)?

The correct choice is the type of router that directly interfaces with external networks and manages the entry and exit of traffic onto the Label Switched Path (LSP) in an MPLS network. This router is tasked with adding or removing labels to packets based on the configured forwarding equivalence classes (FEC).

Edge routers are specifically designed to perform this function by handling traffic from the local area network (LAN) or customer premises equipment (CPE) and making it suitable for transport through the MPLS backbone. When traffic arrives at the edge router, it inspects the packets, assigns appropriate labels, and forwards them into the MPLS network along designated paths, thereby optimizing the flow of data and improving the overall efficiency of the network.

In contrast, other types of routers, such as core routers, primarily manage the data pathways within the MPLS backbone without directly interfacing with external traffic. Label Switch Routers are a more general term that refers to any router that can switch labels within the network, and access routers typically serve to connect end-user devices to the local network rather than handling MPLS-specific label switching directly.