EIGRP Opcode 3: Query Packets

Opcode 3: Query Packets

• As per RFC 7868: Section 4.2, Opcode 3 is assigned to a specific type of EIGRP packet. These packets are sent when a route in the EIGRP network goes into the 'Active' state. The 'Active' state signifies that EIGRP is actively searching for a feasible route to a destination.

• Query packets are sent using multicast communication. This means that they are broadcasted to a select group of routers in the network.

• A crucial feature of Query packets is their reliability. They are always sent reliably, ensuring their secure delivery to the intended recipients.

• Another important aspect is that when a router sends a Query packet, it anticipates receiving an acknowledgment ('ACK') as well as a 'Reply' from the receiving router. This acknowledgment confirms the successful receipt of the Query packet.

Verification:

To monitor and troubleshoot EIGRP networks that involve Query packets, the following verification commands are particularly useful:

• show ip eigrp interfaces [interface] [detail]: This command displays detailed information about EIGRP interfaces, including their configuration and status. It's a valuable tool for inspecting the state of interfaces involved in the EIGRP process.

• show ip eigrp neighbor [detail]: Use this command to view comprehensive information about EIGRP neighbors. It provides insights into neighbor relationships, including IP addresses, hold times, and state.

• debug eigrp packets [query] [detail]: Enabling this debug command allows you to closely monitor EIGRP Query packets and their associated details. It can help in diagnosing network issues related to Query packets.

• show ip eigrp traffic: This command provides an overview of EIGRP traffic statistics, including the count of various EIGRP packet types. It's useful for assessing overall EIGRP traffic patterns.

• show ip protocols: When you need to examine the details of IP routing protocols in use, including EIGRP, this command offers a comprehensive view. It provides information on routing protocol settings and parameters.

In conclusion, Opcode 3 in EIGRP, represented by Query packets, serves a critical role in the EIGRP network when routes go into the 'Active' state. These packets are sent reliably via multicast communication and are expected to receive acknowledgments and replies. To maintain and troubleshoot EIGRP networks effectively, the provided verification commands offer valuable insights and diagnostic capabilities.