Cisco Certified Network Associate (CCNA) Practice Exam

EIGRP supports multiple network layer protocols through what mechanism?

1. Network Layer Options

2. Protocol Dependent Modules

3. Layer 3 Protocol Emulators

4. Dynamic Routing Updates

The correct answer is: Protocol Dependent Modules

EIGRP, or Enhanced Interior Gateway Routing Protocol, supports multiple network layer protocols through the use of Protocol Dependent Modules (PDMs). PDMs enable EIGRP to manage different network layer protocols such as IPv4, IPv6, and AppleTalk by providing specific handling logic for each protocol. This design allows EIGRP to be versatile, as it can efficiently route packets across various types of network communications without requiring significant changes to the core EIGRP implementation. Each PDM is responsible for processing routing information, managing neighbor relationships, and facilitating the routing table updates relevant to its respective protocol. In the context of EIGRP's functionality, this modularity means that new protocols can be supported without overhauling the entire routing protocol. It provides a significant advantage in complex networks where different networking protocols are in use. PDMs thus play a vital role in EIGRP's capability to function across diverse environments while maintaining high performance and scalability.