What type of router only swaps the outer label when forwarding traffic in an MPLS network?

In an MPLS (Multiprotocol Label Switching) network, the component responsible for forwarding traffic by swapping the outer label is the core router. Core routers operate within the backbone of the network, where they handle high-speed data transfer and efficiently manage traffic flows. When a data packet is received, the core router examines the outer label, makes forwarding decisions based on it, and then replaces that outer label before sending the packet to the next hop.

This label-switching process allows for rapid forwarding without the need for deep packet inspection, which typically slows down traditional IP routing. Core routers perform this task consistently across the network to maintain streamlined communication and improve overall efficiency.

The other options do not perform this specific function in the same way. Switches operate at Layer 2 of the OSI model, primarily using MAC addresses for forwarding decisions, while bridges also deal with Layer 2 traffic. Edge routers function at the boundary of an MPLS network, often dealing with label distribution and interfacing between the MPLS network and external networks, but their role is not limited to simply swapping outer labels in the same manner as core routers. Thus, the primary role of label swapping in the context described aligns with core routers.