Network Kings

Multi-Access Year Deal

Get 55+ courses now at the best price ever! Use Code:    MULTIYEAR

d :
h :
m
Claim Offer
Consult Us

eigrp in networking

What is EIGRP in Networking? Explained

by
eigrp in networking
eigrp in networking

EIGRP in networking, also called Enhance Interior Gateway Routing Protocol (EIGRP), works on layer 3 of the OSI model and helps find the best path. It is an updated version of the IGRP protocol. EIGRP used to be a Cisco Proprietary protocol but it became an Open standard protocol and can be configured on devices other than Cisco. Administrative distance for EIGRP is 90 for internal routes and 170 for external routes. EIGRP uses protocol number 88.

EIGRP in networking is an advanced distance vector routing protocol, also called hybrid routing protocol, that uses the properties of Distance vector routing protocol as well as link-state routing protocol.

In the Enhanced Interior Gateway Routing Protocol (EIGRP), multicasting efficiently exchanges routing information between routers within the same Autonomous System (AS). EIGRP uses a specific multicast address for this purpose. The multicast address used by EIGRP for IPv4 is 224.0.0.10. In the case of IPv6, EIGRP uses the multicast address FF02::A.

EIGRP routers send their routing updates and queries to this multicast address, allowing other routers in the same EIGRP AS to receive and process the routing information. Multicasting helps reduce unnecessary network traffic by ensuring that EIGRP updates are only sent to routers interested in receiving them, which is especially important in larger networks.

What are the features of EIGRP in Networking?

The features of EIGRP in Networking are as follows- 

  • EIGRP uses a Diffusion Update Algorithm (DUAL). This algorithm helps EIGRP routers to perform rapid convergence when changes occur in the network. EIGRP also sends updates when there is a change in the network topology, unlike traditional distance routing protocol that sends updates periodically. This helps EIRGRP become efficient and saves bandwidth. 
  • EIGRP supports Variable Length Subnet Mask (VLSM) and Classless Inter-Domain Routing (CIDR) which allows efficient use of IP Address. 
  • EIGRP supports route summarization which helps to reduce the size of the routing table and minimize the amount of routing information exchanged between routers. 
  • EIGRP uses loop prevention mechanisms such as the split horizon to prevent routing loops in the network. 

What are the types of EIGRP Packets?

Enhanced Interior Gateway Routing Protocol (EIGRP) different types of packets to facilitate the exchange of routing information and maintain neighbour relationships between routers within the same Autonomous System (AS).

  • Hello Packet

This packet is used for neighbour discovery and to maintain the neighbourship after it is established. These packets are sent by EIGRP routers periodically. When 2 routers receive the EIGRP Hello Packet, they become neighbours. 

  • Update Packets

These packets are used to update neighboring routers about the changes in the network topology. These packets are only sent when there is a change in network topology like route deletion, new routes addition, link failure, metric update, etc. 

  • Query packet

Query packets are used to request more specific information about a particular route. When a router detects a topology change and updates its routing table, it may send Query packets to its neighbors to ask for more details about routes that have become unreachable. This helps in resolving potential routing inconsistencies. 

  • Reply Packets

Reply packets are sent in response to Query packets. When a router receives a Query for specific routing information, it responds with a Reply packet, providing the requested details about the route. 

  • Acknowledgment (ACK) Packets

Acknowledgment packets are used to confirm the receipt of Update, Query, and Reply packets. When a router receives one of these packets from a neighbor, it sends back an ACK to acknowledge receipt. This helps ensure that the packets are delivered successfully. 

  • RTP (Reliable Transport Protocol) Packets

EIGRP uses RTP as its transport protocol to provide reliable and ordered delivery of packets. RTP encapsulates EIGRP Hello, Update, Query, Reply, and ACK packets for transmission between routers. It ensures that packets are delivered without duplication, loss, or out-of-order delivery.

What are EIRGP tables?

EIGRP uses some tables to maintain routing information, find the best path, and recalculate the paths when the primary path goes down for some reason. The tables used by EIGRP are:- 

  • Neighbour Table

The EIGRP Neighbour Table, keeps information on neighbouring routers with which the local router has formed EIGRP neighbour relationships. It contains information about the IP addresses of neighbours, their interface, hold timers and other parameters required for neighborship maintenance. 

The command used to see neighbor table: –  R#show ip eigrp neighbors 

  • Topology Table

It keeps detailed information about routes learned from EIGRP neighbours. This table contains entries for all known routes, including feasible successors and any potential backup routes. It includes information such as the destination network, metrics, and the state of the route (active, passive, or stuck in active). It basically includes the information of the whole topology configured within the EIGRP Autonomous System (AS). 

The command used to see the topology table: – R#show ip eigrp topology  

  • Routing Table

The Routing Table also called the global routing table contains the best routes to reach various network destinations within the EIGRP Autonomous System (AS). This table is derived from the Topology Table and is used for making forwarding decisions. EIGRP selects the routes with the lowest composite metric values to populate the Routing Table.

Basic EIGRP Configuration 

 

Syntax: – 

 

R(config)#router eigrp <Process ID> 

R(config-router)#network <Network IP> 

R(config-router)#no auto-summary :- Used to disable auto summarization of routes. 

 

Let us look at the below given topology: – 

routing table

R1(config)#router eigrp 1
R1(config-router)#network 192.168.13.0
R1(config-router)#no auto-summary

R2(config)#router eigrp 1
R2(config-router)#network 192.168.13.0
R2(config-router)#network 192.168.34.0
R2(config-router)#no auto-summary

R3(config)#router eigrp 1
R3(config-router)#network 192.168.34.0
R3(config-router)#no auto-summary

Verification: – 

 

R1#show ip eigrp topology  

 

IP-EIGRP Topology Table for AS 1/ID(192.168.13.1) 

Codes: P – Passive, A – Active, U – Update, Q – Query, R – Reply, 

r – Reply status 

 

P 192.168.13.0/24, 1 successors, FD is 2816 

via Connected, GigabitEthernet0/0/0 

P 192.168.34.0/24, 1 successors, FD is 2816 

via Connected, GigabitEthernet0/0/1 

 

 

 

 

 

R2#show ip route  

 

 

Codes: L – local, C – connected, S – static, R – RIP, M – mobile, B – BGP 

D – EIGRP, EX – EIGRP external, O – OSPF, IA – OSPF inter area 

N1 – OSPF NSSA external type 1, N2 – OSPF NSSA external type 2 

E1 – OSPF external type 1, E2 – OSPF external type 2, E – EGP 

i – IS-IS, L1 – IS-IS level-1, L2 – IS-IS level-2, ia – IS-IS inter area 

* – candidate default, U – per-user static route, o – ODR 

P – periodic downloaded static route 

 

Gateway of last resort is not set 

 

192.168.13.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.13.0/24 is directly connected, GigabitEthernet0/0/0 

L 192.168.13.2/32 is directly connected, GigabitEthernet0/0/0 

192.168.34.0/24 is variably subnetted, 2 subnets, 2 masks 

C 192.168.34.0/24 is directly connected, GigabitEthernet0/0/1 

L 192.168.34.1/32 is directly connected, GigabitEthernet0/0/1 

What is EIGRP in Networking?

by
eigrp protocol
eigrp protocol

Known as the Enhanced Interior Gateway Routing Protocol (EIGRP), it is a hybrid routing protocol. In this blog, we will learn about the EIGRP protocol and how it works.

In the Previous blog, we learned about the Routing Information  protocol (RIP), a distance-vector interior gateway protocol. I definitely recommend you go through that blog before Jumping to this blog. 

Here, we are about to learn about the EIGRP protocol and how it works. we will know how EIGRP chooses the best route to send the packets. After that, we will also learn about the different packet types that the EIGRP uses for the management of the sessions. At last, we will learn a few benefits of the EIGRP.

Without any further ado, let us begin learning about EIGRP in networking in detail!

What is Meant By EIGRP?

You will find out that many things about EIGRP are similar to RIP. Let us begin learning about some key features of EIGRP:

  • The term EIGRP is an acronym that stands for Enhanced Interior Gateway Routing Protocol.
  • It is an improved version of the older Interior Gateway Routing Protocol (IGRP).
  • EIGRP was previously a Cisco-owned protocol. However, Cisco has now made it an open-standard protocol. Therefore, any vendor can use it now on their equipment!
  • EIGRP is considered an ‘advanced’ or ‘hybrid’ distance vector routing protocol.
  • It improves many basic operations of RIP which is its fellow distance vector routing protocol.
  • It is way faster than RIP in reacting to the changes needed in the network.
  • It does not have a  hop count limit of 15 like RIP. Therefore, it supports very large networks.
  • It sends messages using the multicast address 224.0.0.10.
  • EIGRP can be deployed on both IPv4 and IPv6 Internet Protocol networks. It can also be deployed on networks such as Novell Internetwork Packet Exchange.
  • EIGRP is the only Interior Gateway Protocol (IGP) that can perform unequal-cost-load-balancing. It performs equal-cost-load-balancing (ECMP) load balancing over 4 paths like RIP by default.
  • EIGRP can even load balance on the basis of the proportion of their bandwidth. Therefore, more traffic will be sent over to the paths with lower metric as they are faster.
  • Less traffic will be sent to the paths with higher metric as they are slower.

EIGRP is a wonderful protocol. However, it is mostly used in Cisco devices, therefore, it is not as widely used as OSPF.

How Does The EIGRP Choose The Best Path?

Unlike other routing protocols, EIGRP uses four major metrics to choose the best path to transmit the packets. These metrics are:

  • Bandwidth
  • Delay
  • Load, and 
  • Reliability

The default metric used by EIGRP is bandwidth and delay. 

EIGRP uses the following table for route discovery:

  • Neighbor table
  • Topology table
  • Route table
  • Successors
  • Feasible successors

Now, let’s see how this table works step-by-step.

1. Neighbor Table:

  • The neighbor table is used to store the condition of the directly connected neighbors.
  • This means that whether the directly connected router is active or non-active, the neighbor table is going to store the information anyway.

For example, if two routers are connected to each other directly, both routers are going to send the ‘Hello’ packets to each other after every 5 seconds. These two routers consider each other alive as long as this exchange of packets continues.

If the router is not able to receive the hello packet in 5 seconds, it realizes that the link is down and forwards this information to another connected router. In such a way, all the routers are updated about the link failure of a particular router in the network.

2. Topology Table:

  • This table is used to store the advertisements of the destinations by the neighbors.
  • The advertisement includes:
    • The destination address
    • The neighbor that is linked to the destination
    • The metrics used by the neighbor to the destination

For example, if three routers are connected to each other in a linear form and the first router wants to reach the third router, it is not going to receive any advertisement from the third router. In fact, it will receive an advertisement from the second router. 

This is because the second router knows the best route to reach the third router and the first router knows the best route to reach the second router. This is how all the routers are configured with EIGRP to calculate and update the router to their routing table.

3. Routing Table:

  • This table is used to store all the possible routes to reach the destination.
  • This is the main function of the routing table.

4. Successors:

  • The successor is the path with the best metric.
  • This means that the successor is the best available route in the routing table to reach the destination and the router chooses this route first.

5. Feasible Successors:

  • It is considered a backup route.
  • If the path distance is less than the original path to reach the destination, it is considered feasible.
  • When the successor path is invalid or inactive, it becomes the first choice.
  • It is the second fastest available route to reach the destination.

The algorithm which determines the most efficient and reasonable routes to reachable destinations is the Diffusing Update Algorithm (DUAL). This is decided on the basis of the distance and whether the destination path is loop-free.

What Packages are Used By EIGRP?

EIGRP uses 5 packages to pass messages and allow the management of the sessions. These are:

  • HELLO packets
  • QUERY packets
  • REPLY packets
  • REQUEST packets
  • UPDATE packets

What are the Benefits of EIGRP?

The EIGRP protocol has the following benefits:

  • It has a faster convergence.
  • There is no need to update the routing tables by hand.
  • It has a low network resource usage as it only sends HELLO packets when the network is stable.
  • It either uses unequal-cost-load-balancing or equal-cost multipath balancing to use links more efficiently.
  • It is loop-free therefore, it improves video and voice quality.

Conclusion

EIGRP is the new-age Interior Gateway Protocol (IGP) that has a faster convergence. Its highlighting feature is the unequal-cost-load-balancing that in return, reduces CPU usage.

However, EIGRP is more of a Cisco proprietary even though some of its features are open-standard. OSPF is considered over EIGRP!

Stay tuned for learning more Protocols such as BGP in the CCNA series

Happy learning!