Cisco Certified Network Associate (CCNA) Practice Exam

In the #show eigrp neighbors output, what does uptime refer to?

1. The total time since the router started

2. The time since the adjacency was established

3. How long the neighbor has been reachable

4. The duration of the last successful transmission

The correct answer is: The time since the adjacency was established

In the context of the #show eigrp neighbors command, uptime specifically refers to the duration since the EIGRP neighbor adjacency was established. When two EIGRP routers form a neighbor relationship, they exchange hello packets to confirm their connectivity and establish a route table. The uptime metric is a key indicator of how long the routers have been communicating with each other since the adjacency was formed. This metric is vital for network administrators as it reflects the stability and reliability of the connection between the two routers. A longer uptime typically indicates a stable relationship, while a shorter uptime may suggest recent reconnections, which could be due to network issues or configuration changes. Other options, while related to network operations, do not accurately describe uptime in the #show eigrp neighbors context. For instance, the total time since the router started pertains to the overall operational duration of the router itself, not the specific adjacency. Similarly, the notion of how long a neighbor has been reachable or the duration of the last successful transmission do not align with the distinct definition of uptime in EIGRP neighbor relationships. Thus, the clarity of the term "uptime" as it relates specifically to the EIGRP adjacency establishes the correctness of the answer.