Cisco Certified Network Associate (CCNA) Practice Exam 2026 - Free CCNA Practice Questions and Study Guide

For EIGRP (Enhanced Interior Gateway Routing Protocol) routers to communicate successfully, they must be configured on the same subnet. This allows the routers to directly exchange routing information over the same link layer, which is essential for establishing neighbor relationships.

Matching K values is also vital because EIGRP uses these values to calculate the composite metric used for routing decisions. If the K values are different across routers, they will compute different metrics for the same route, leading to inconsistent routing updates and potential routing loops.

Correct authentication is significant for ensuring that only authorized routers can participate in the EIGRP process. This security measure prevents unauthorized devices from injecting incorrect routing information into the network.

In summary, the three crucial requirements for EIGRP routers to communicate effectively are being on the same subnet, having matching K values, and implementing correct authentication. This ensures that they can form neighbor relationships, calculate consistent routing metrics, and maintain secure communication.