Which of the following is a Distance Vector routing protocol?

The correct answer is EIGRP, as it is categorized as a hybrid routing protocol that incorporates both Distance Vector and some Link State characteristics. It uses the router's knowledge of the network, including metrics like bandwidth, delay, reliability, and load, to calculate the best path for data to travel. EIGRP employs the Diffusing Update Algorithm (DUAL) to provide a loop-free environment and faster convergence, characteristics that are often associated with Distance Vector protocols.

Distance Vector protocols communicate their routing table updates to their neighbors, which is a feature of EIGRP although it also retains features typical of Link State protocols. This hybrid nature enables it to efficiently manage routing tables and the paths taken by data packets across a network, making it effective in larger and more complex network environments.

The other protocols listed—OSPF, BGP, and IS-IS—are categorized as Link State (OSPF and IS-IS) or Path Vector (BGP) protocols. Link State protocols maintain a complete view of the network topology, while Path Vector protocols use a mechanism of route advertisement along with path information to ensure routing decisions. Understanding these distinctions helps in identifying how different protocols operate within different networking environments.