Updated March 18, 2023
Introduction to EIGRP Interview Questions
EIGRP is the latest distance-vector routing protocol that is applied to computer networks for automation to make decisions on routing and configuration. This protocol is developed by cisco systems as a registered algorithm, available only for cisco routers. EIGRP is expanded as an Enhanced interior gateway routing protocol. It is also called a diffused update algorithm to define the shortest path. It is also measured as a hybrid routing protocol since it has the attributes of link-state routing protocols and distant vector. EIGRP supports classless routing, route summarization, load balancing, and VLSM. In this topic, we are going to learn about EIGRP Interview Questions.
Some of the most important EIGRP Interview Questions that are frequently asked in an interview are as follows:
Part 1 – EIGRP Interview Questions(Basics)
This first part covers basic EIGRP Interview Questions and Answers
1. Explain the various tables used in EIGRP?
The three different tables applied in EIGRP are a neighbor table, topology table, and route table.
The neighbor table is filled with a neighbor relationship that is tracked in a table based on EIGRP routing and activity of convergence. The interface and address of the neighbor are introduced and recorded as a fresh entry of the neighbor table, whenever a new neighbor is introduced. The table is validated for reliable and sequential delivery of packets.
Topology table: This is a reference table for routing traffic in a network for routers. This routing table in the automatic system is available such as a router position in this table. Each router is based on the routing protocol and manages a topology table for every configured network protocol. The routes lead to destination port based on the topology table.
Route table: The paths of a particular source and destination are stored in routing tables. The data in the network topology is immediately placed around it. The main goal of routing protocols is to construct the path of the routing table. Network id, packets cost, and path of the packet and details of the next-hop details are available in the routing table.
2. Explain the different types of packets in EIGRP?
The different packets available in EIGRP are hello packets, update packets, query packets, reply packets, and ack packets. Hello, packets maintain the EIGRP neighborship when its discovered. If the router fails to get a hello packet within the estimated time, the particular router will be acknowledged as dead. If any new neighbor packet is discovered, updated packets are transmitted, so that the topology table is updated by the nearby router. Update packets are transmitted reliably in a single direction. Whenever the destination turns into an active state, query packets are transmitted. Query packets work as multicast and responses are often sent to query to indicate the originator which does not need to go into an active state. If the destination turns into an active state, reply packets are transmitted. Reply packets are unicast to the origin of the query and sending of reply packets is trustworthy. The act packets use to find the status of transmission. If any hello packets sent without information is considered as acknowledgment. The non-zero acknowledgment value is the unicast address that is sent by acks.
3. What are the conditions for EIGRP neighbours?
The source and destination routers must be in the same primary subnet and should be configured to use the same k-values. The source and destination router should have the identical authentication configuration with boundaries facing each other in parallel. They should not be passive.
Let us move to the next EIGRP Interview Questions.
4. Is it mandatory to apply the eigrp log-neighbor-changes command when configuring eigrp?
It is mandatory to use this command for easy determination and reduction of troubleshooting time.
5. Whether EIGRP support secondary addresses?
It doesn’t support secondary addresses. Since EIGRP always searches data packets from the primary address, cisco advises configuring routers on considering subnet with the subnet of similar primary addresses. Because routers don’t form eigrp neighbors over secondary networks. If any routers didn’t adjust to primary IP addresses, issues can occur with adjacent neighbors.
6. List the merits of EIGRP over other routing protocols?
It has advanced distance vector and routes IP’s, ipx, AppleTalk and DECnet. It reacts partially when any routing changes occur in metrics such as bandwidth, reliability, load, hop count, size of the maximum transmission unit and transmission delay. The hello timer operates with 1 second on ethernet and sixty seconds on non-broadcast.
Part 2 – EIGRP Interview Questions and Answers (Advanced)
Let us now have a look at the advanced EIGRP Interview Questions
7. Defined advertised distance?
It is also called a reported distance which is the distance between the given neighbor and destination router. The feasible distance is measured from the current router to the destination.
8. Define successor?
It is a routing path whose reported distance is minimum than the possible distance, and it is also mentioned as a backup route. EIGRP will maintain six possible successors in the topology table. The successor with best and efficient metrics is positioned to the routing table.
9. Explain ‘” stuck inactive”?
EIGRP replies a stuck in active message means that it has not received a reply to its query. EIGRP transmits queries when any route is lost or if its unable to find the path or if any path doesn’t occur in the topology table. The stuck in the message is activated by two sequential events, if the path mentioned is erased and if it is unable to locate.
Let us move to the next EIGRP Interview Questions.
10. Mention the type of authentication supported by EIGRP?
EIGRP provides md5 authentication for routing updates from routing protocols. The md5 key in every EIGRP packet protects the injection of false routing message from unapproved sources to prevent any malware attack
11. Define ‘” graceful shutdown”?
It is a special feature that supports the fast convergence of networks. By using a graceful shutdown, a goodbye message is broadcasted by EIGRP routing to shut down the process. It is made to announce the adjacent peers about the changes in topology
12. What is the maximum path load-balanced by EIGRP?
Load-balancing is the ability of a router to evenly distribute the traffic all over the network with router ports with the same distance and value of destination address. Load balancing maximizes the utilization of network segments to increase the effective bandwidth of the network.
EIGRP works on Reliable Transport Protocol (RTP) for the transmission of packets. If the packet sent is not delivered it has the options to send again. It is simple with four components protocol-dependent module, RTP, Neighbour discovery and recovery model, and diffusing update algorithm.
This has been a guide to EIGRP Interview Questions and Answers. Here we have covered few commonly asked interview questions with their detailed answers so that it helps candidates to crack interviews with ease. You may also look at the following articles to learn more –