Which of the following is NOT a characteristic of an Interior Gateway Protocol (IGP)?

An Interior Gateway Protocol (IGP) is specifically designed for routing within a single autonomous system (AS). One of the key characteristics of IGPs is that they are used to manage routing information among routers that are part of that AS. They optimize how data packets are forwarded based on the most efficient paths and adapt to changes in the network topology.

The option stating "exchanges external routing information" is not a characteristic of an IGP because this role is typically handled by External Gateway Protocols (EGPs), such as BGP (Border Gateway Protocol). EGPs are responsible for exchanging routing information between different autonomous systems, enabling interoperability between various networks.

In contrast, IGPs like OSPF (Open Shortest Path First) and RIP (Routing Information Protocol) focus on internal routing processes, managing routes and updates within a single administrative domain, thus enhancing the efficiency of routing within that environment. They are designed for smaller networks and handle dynamic routing updates effectively but do not deal with routing information external to the autonomous system.