Top 15 Most Asked EIGRP Interview Questions and Answers

Get equipped with these 15 most asked EIGRP interview questions and answers to perform better in your upcoming interview. These questions are curated by our experts, some of the most talented minds in the networking field.

The most recent distance vector routing protocol is EIGRP, Enhanced Interior Gateway Routing Protocol. It utilizes the DUAL (Diffused Update Algorithm) to determine the shortest path. It is also referred to as a hybrid routing protocol since it possesses elements of distance vector and link-state routing protocols.

We will introduce you to the top EIGRP interview questions that are frequently asked in most interviews.

EIGRP Interview Questions and Answers

Here are the EIGRP interview questions:

Question 1 - What are the requirements for Neighborship in EIGRP?

Answer – To become successful neighbours, these are the requirements that must match for routers in a hello packet:

• Autonomous System number
• Authentication
• K-values
• Use of Primary address

A static neighborship should be defined on both sides. These are the requirements to form a neighborship in EIGRP.

Question 2 - Which tables are maintained by EIGRP routers?

Answer - EIGRP router stores routing and topology information in Three tables:

• Neighbour Table- Store information about EIGRP neighbours.
• Topology Table- Store routing information which is learned from neighbours' routers.
• Routing Table- Store the best path to all networks.

Question 3 - Why "no auto-summary command" is used in EIGRP?

Answer - EIGRP does not disclose the subnet mask with the routing information by default, behaving instead like a classful routing protocol. No auto-summary command will guarantee that EIGRP sent the routing information and the subnet mask information.

Question 4 - What are the EIGRP Hello & Hold Timer?

Answer - Hello Timer: Every five seconds (hello time), the router will broadcast a hello to its neighbours.

Hold Timer: If the router does not hear from a neighbour after 15 seconds, it will assume that the link is down and terminate the neighbour relationship.

Question 5 - What is the Feasible distance?

Answer - The distance (metric) between the source and the destination network is known as Feasible distance. Given that it is the most effective way to reach a remote network, the route with this metric will be included in the routing table.

Question 6 - What are advertised Distance & Reported Distance?

Answer - The advertised distance is the distance separating a neighbour router from the target network. The reported distance is a destination network metric that a neighbour has reported.

Question 7 - What are the EIGRP packet types?

Answer – Here are the different EIGRP packet types:

• Hello — Used for the discovery of EIGRP neighbours and for detecting when a neighbour is no longer available
• Request — Used to request one or more neighbours for specific information
• Update — Used when communicating with other EIGRP neighbours to send routing and reachability information
• Query — Sent out during convergence to look for a different route
• Reply — Sent in response to a query packet

Question 8 - What are the EIGRP named mode?

Answer - The new method of configuring EIGRP is called named mode. Under the router mode, this mode enables the hierarchical entry of EIGRP configurations. Multiple address families and autonomous system number combinations are possible for each named mode setup.

Question 9 - What are EIGRP variance values?

Answer - Through Variance Command, EIGRP provides a method to load balance over cost-inequal pathways. The local best metric is multiplied by the variance (a number between 1 to 128), which includes the routes with a lesser or equivalent metric. When the Variance value is set by default to 1, equal-cost load balancing is indicated.

Question 10 - What is the EIGRP Convergence?

Answer - Regarding convergence, EIGRP maintains a backup route. In case the current path to the destination network fails, it can immediately switch over to using the backup route, the feasible successor leading to faster convergence.

Question 11 - How do I fix EIGRP stuck in active?

Answer – The router sends out query messages on all EIGRP-enabled interfaces and attempts to identify a new path to the network if the successor path is lost and there is no feasible successor path available. For that route, it is in an active status.

The router is now awaiting a response from its neighbours. If a response is absent for three minutes, no neighbours respond, and the router stays in the active state. In this instance, the router re-established its neighbourly connection with the router that had not returned its query messages.

 Two approaches are utilised to resolve this issue:

• Router summarization
• EIGRP Stub

The following command is used to unstick the active timer that has become stuck:

Router(config-router)# timers active-time disable

Question 12 - What is a leak map in EIGRP?

Answer – Using the leak-map, you can only advertise a specific prefix within the bounds of a summary advertisement and the summary itself. In essence, all routers are simply running EIGRP 100 with auto-summary turned off.

Question 13 - What is the EIGRP stub router?

Answer - The main goals of the EIGRP stub routing function are to increase network stability and save memory and CPU on local routers. In hub-and-spoke networks, the stub routing function is most frequently employed.

Question 14 - What is the split-horizon in EIGRP?

Answer – The split horizon is a strategy employed by distance vector routing systems to prevent routing loops. The idea is straightforward: a router won't promote a route back onto the interface from where it was learned. On interfaces, split horizon is turned on by default.

Question 15 - Tell me some commands to troubleshoot EIGRP?

Answer – These are the commands that are used to troubleshoot EIGRP:

• #show ip route = It Shows full Routing Table
• #show ip route eigrp = It Shows only EIGRP Routes
• #show ip eigrp neighbours = It Shows EIGRP Neighbours Table
• #show ip eigrp topology = It Shows EIGRP Topology Table

These are our hand-picked top 15 EIGRP Interview questions and answers. If you have some doubts related to the EIGRP topic, then here is the video to clear all your EIGRP doubts and queries.

We wish you all the best for your interview and hope these questions will be helpful. Please do comment in the comment box below to share your views and feedback.

EIGRP is an integral part of our CCNP ENCOR training program, where we teach EIGRP in depth. You visit the CCNP ENCOR page for further details. You can also check out our other training programs if you want to upskill yourself. PyNet Labs is the leading training institute for SD-WAN training.

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EIGRP Interview Questions and Answers FAQs

Question – Which protocol is used by EIGRP?

Answer – The protocol used by EIGRP to establish communication between EIGRP-speaking routers is the Reliable Transport Protocol. The RTP is the Cisco protocol for quickly delivering updates and tracking data reception.

Question – Is EIGRP UDP or TCP?

Answer – EIGRP is neither UDP (User Datagram Protocol) nor TCP (Transmission Control Protocol). It doesn't need a port number to identify traffic and is designed to work on top of layer 3.

Question – What does EIGRP stand for?

Answer – EIGRP stands for Enhanced Interior Gateway Routing Protocol. It is a Cisco proprietary protocol used on a network for automating routing decisions and configuration. It is the advanced distance-vector routing protocol.

Question – What are the basic features of EIGRP? 

Answer – The basic features of EIGRP are as follows: 

• Classless protocol 
• A hybrid routing protocol that uses IP protocol 88. 
• It uses DUAL for loop prevention 
• Reduced Bandwidth usage 
• Communication via RTP 
• VLSM support 
• Both IPv4 and IPv6 supported 
• Rapid convergence 

Question - How does EIGRP Metric Calculation is done?

Answer: This is one of the most asked EIGRP Interview questions, find the answer in this video or read this blog - EIGRP Metric Calculation.