1. What is EIGRP?
EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced distance-vector routing protocol used in computer networks.

2. How does EIGRP work?
EIGRP uses a diffusing update algorithm (DUAL) to determine the best path for routing packets. It calculates the metric of a route based on bandwidth, delay, reliability, and load.

3. What is the administrative distance of EIGRP?
The administrative distance of EIGRP is 90.

4. What are the advantages of using EIGRP?
Some advantages of EIGRP include fast convergence, support for multiple network technologies, load balancing, and support for various routing metrics.

5. What is the maximum hop count in EIGRP?
The maximum hop count in EIGRP is 100.

6. How does EIGRP calculate the metric?
EIGRP calculates the metric by considering bandwidth and delay. It uses a formula that takes into account these two factors and produces a composite metric.

7. What is the EIGRP multicast address?
The EIGRP multicast address is 224.0.0.10.

8. What is the bandwidth-based metric calculation formula in EIGRP?
The bandwidth-based metric calculation formula in EIGRP is 10^7 / minimum bandwidth (in kilobits per second).

9. What is the default update interval in EIGRP?
The default update interval in EIGRP is 5 seconds.

10. What is the purpose of the EIGRP neighbor table?
The EIGRP neighbor table keeps track of neighboring routers with which EIGRP exchanges routing information.

11. How does EIGRP handle unequal-cost load balancing?
EIGRP handles unequal-cost load balancing by using the variance command in its configuration.

12. What are the main EIGRP packet types?
The main EIGRP packet types are Hello packets, Update packets, Query packets, Reply packets, and ACK (Acknowledgment) packets.

13. How does EIGRP handle network convergence?
EIGRP handles network convergence by using its diffusing update algorithm (DUAL), which quickly determines the best route and updates the routing table.

14. What is the difference between distance-vector and link-state routing protocols?
Distance-vector routing protocols, such as EIGRP, determine the best path based on distance or metric. Link-state routing protocols, like OSPF, create a detailed map of the network and calculate the shortest path.

15. How does EIGRP handle loop prevention?
EIGRP handles loop prevention by using a loop-free path selection mechanism based on the feasibility condition.

16. What is the EIGRP metric for a route with a bandwidth of 64 Kbps and a delay of 100 milliseconds?
The EIGRP metric for a route with a bandwidth of 64 Kbps and a delay of 100 milliseconds is 430080.

17. What is the purpose of the EIGRP successor?
The EIGRP successor is the best route selected by DUAL and used for forwarding packets.

18. How does EIGRP handle route redistribution?
EIGRP handles route redistribution by using route redistribution commands and policies to exchange routes with different routing protocols.

19. What is the difference between EIGRP and OSPF?
EIGRP is a distance-vector routing protocol, while OSPF is a link-state routing protocol. EIGRP uses a simpler metric calculation and is more suitable for smaller networks, while OSPF is better suited for larger networks.

20. What can cause EIGRP neighborship not to form?
EIGRP neighborship may not form due to mismatched authentication settings, connectivity issues, or different autonomous system numbers (ASNs) on neighboring routers.

1. What is EIGRP?
EIGRP (Enhanced Interior Gateway Routing Protocol) is an advanced distance-vector routing protocol used in IP networks. It is a Cisco proprietary routing protocol.

2. What are the advantages of EIGRP over other routing protocols?
EIGRP offers the following advantages:
– Fast convergence
– Low bandwidth and CPU utilization
– Support for both IP and IPX
– Load balancing and equal cost path routing
– Support for VLSM (Variable Length Subnet Masking)
– Authentication of routing information

3. How does EIGRP calculate a metric?
EIGRP uses bandwidth, delay, reliability, and load in its metric calculation. Bandwidth and delay are the primary factors determining the metric.

4. What is the default administrative distance of EIGRP?
The default administrative distance of EIGRP is 90.

5. What is Feasible Distance (FD) in EIGRP?
Feasible Distance (FD) is the best metric or cost of a route to reach a destination. It represents the metric of the neighbor router plus the cost of the link between the local and neighbor router.

6. What is Advertised Distance (AD) in EIGRP?
Advertised Distance (AD) is the metric or cost of the route as advertised by the neighbor router.

7. How does EIGRP perform load balancing?
EIGRP performs load balancing by considering multiple paths with equal cost (feasible successors) and using them to forward traffic.

8. How does EIGRP converge faster than other routing protocols?
EIGRP uses the Diffusing Update Algorithm (DUAL) to converge faster. It uses three tables: the Neighbor Table, the Topology Table, and the Routing Table for efficient routing updates.

9. What are the EIGRP packet types?
EIGRP uses the following packet types:
– Hello packets
– Update packets
– Query packets
– Reply packets
– ACK packets

10. What is the purpose of EIGRP Hello packets?
Hello packets are used for neighbor discovery, acknowledgment, and maintaining neighbor relationships.

11. What is the significance of the EIGRP AS (Autonomous System) number?
The EIGRP AS number is a unique identifier used to group routers into autonomous systems. It ensures that EIGRP routers only form neighbor relationships within the same AS.

12. How does EIGRP handle route authentication?
EIGRP supports route authentication using MD5 (Message Digest 5) encryption. The same pre-shared key must be configured on all routers within the same AS.

13. How can you enable EIGRP authentication on an interface?
To enable EIGRP authentication on an interface, use the ‘ip authentication mode eigrp md5′ command. Additionally, the ‘ip authentication key-chain eigrp ‘ command is used to specify the keychain to implement authentication.

14. What is EIGRP Stub Routing?
EIGRP Stub Routing is a feature that allows a stub router to advertise default routes to its neighbors. It reduces the query range and improves network stability.

15. What is EIGRP Wide Metric?
EIGRP Wide Metric is an extended metric used to support larger networks and increase scalability. It allows for metric values beyond the traditional 1-10,000 range.

16. How do you configure EIGRP summarization?
To configure EIGRP summarization, use the ‘ip summary-address eigrp ‘ command on the interface of the router that connects to multiple subnets.

17. What is EIGRP Frame Relay Hub-and-Spoke configuration?
EIGRP Frame Relay Hub-and-Spoke configuration is used when a central router (hub) connects to multiple remote sites (spokes) over a frame relay network. It involves configuring subinterfaces on the hub router and using EIGRP to establish dynamic routing.

18. How does EIGRP support Equal Cost Path (ECP) load balancing?
EIGRP performs Equal Cost Path (ECP) load balancing by installing multiple routes with the same metric in its routing table. It automatically computes and forwards traffic across multiple paths.

19. What is the maximum hop count for EIGRP?
The maximum hop count for EIGRP is 100.

20. How do you monitor EIGRP operations and troubleshoot issues?
To monitor EIGRP operations and troubleshoot issues, you can use the ‘show ip protocols’, ‘show ip eigrp neighbors’, ‘debug eigrp packets’, and ‘debug eigrp events’ commands. Additionally, tools like syslog and SNMP can help in monitoring and alerting.