EIGRP INTERVIEW QUESTIONS

EIGRP- Enhanced Interior Gateway Routing Protocol - Interview Questions

What is EIGRP?

EIGRP (Enhanced interior Gateway Routing Protocol) is dynamic routing protocol helps the 

routers to exchange the routing information’s. This is Hybrid protocol. Cisco proprietary 

protocol. Only works in cisco routers. Hybrid means – (Link stage and Distance vector

process) – First time only send full updates to other router after that changes in topology

table that time only it will update to other routers.

Autonomous No for administrative convenience

Metric – Bandwidth, delay, reliability, load, MTU…

Lowest Metric is called Successor

Administrative Distance 90.

What are the tables in EIGRP?

Three tables in EIGRP:

(1). Route table:routing table contains the routing information (best route) – lowest metric 

value called successor. [ first bast path store in route table. primary information called 

successor.

(2). Topology Table: best route but less desirable but still valid – Feasible successor

(Backup Router). Loop free alternate path called feasible successor.

keep both primary and backup information stored in topology table.

Feasible successor (backup router information).

FS= Reporting Distance (Advertise distance)< Feasible Distance of Successor

FS For Loop preventing 

(3). Neighbors table: Contains the Neighbors information. (Discover, learn the address and 

store information).

What are the packets in EIGRP?

Hello, Update, Query, Reply and Acknowledge.

Hello : Hello packets send every 5 seconds for keep alive with the help of multicast address 

224.0.0.10

Update : if any changes in the topology table it will update. (sending the routing table with 

updates)

Query : For request (requesting specify route information)

Reply : Reply for the Query

Acknowledge : finally acknowledge

What is active and passive in EIGRP?

Active: Active means bad router. It’s not a valid router. Query send to find the backup

router.To get Feasible Successor (looking for backup router).

Passive: Good. Working fine without any problem.

Tell me EIGRP advantages?

It’s using DUAL algorithm (used for to find best path as well as loop free), Support VLSM 

(variable Length subnet Mask), Auto summarization at any point, Unequal load balancing,

fast convergence, Link goes down Process with another best path. 

How to configure summarization on specific interface in EIGRP?

Auto Summarization or manual summarization at any interface or

specific interface. Default auto summarization enabled. 

To disable use command:

# No auto-summary

# interface s0/0

#ip summary-address EIGRP 7 192.168.1.0 255.255.252.0 (subnet mask, AD

administrative Distance).

#ip summary-address EIGRP 7 0.0.0.0 0.0.0.0 

What is use of variance Command in EIGRP?

Variance command used for set-up unequal cost load balancing assigning variance 2.

#router EIGRP 7

# Variance 2


What are the types of authentication will support EIGRP?

MD 5 Authentication between two routers while routing updates).