Cisco Certified Network Associate (CCNA) Practice Exam

What does the Seq number indicate in the #show eigrp neighbors output?

1. The total number of neighbors connected

2. The last sequence number of updates from the neighbor

3. The sequential order of advertisement messages

4. The count of successful transmissions

The correct answer is: The last sequence number of updates from the neighbor

The Seq number in the output of the #show eigrp neighbors command indicates the last sequence number of updates received from the neighbor. In Enhanced Interior Gateway Routing Protocol (EIGRP), sequence numbers are crucial for tracking the updates being sent and received between routers. Each time a router sends an update to its neighbors, it increments its sequence number. This numbering helps ensure that routers can keep track of which updates they have processed and which ones are new. By checking the Seq number, network administrators can determine whether all updates have been successfully received from a neighbor and identify any missing updates that might require attention. This function of requiring updates to have a higher sequence number before being considered valid is fundamental to maintaining synchronization and preventing routing loops within the EIGRP protocol. In this context, the other options do not apply, as the Seq number does not indicate the total number of neighbors connected, the sequential order of advertisement messages, or the count of successful transmissions. Each of these aspects pertains to different elements of EIGRP monitoring and performance tracking but does not directly relate to the purpose of the sequence number.