What are the differences between EIGRP and BGP?

Let us understand the concepts of Enhanced Interior Gateway Routing Protocol (EIGRP) and Border Gateway Protocol (BGP) before learning the differences between them.

Enhanced Interior Gateway Routing Protocol (EIGRP)

It is the enhanced version of IGRP protocol. It consists of all the features which IGRP does and also supports some ad-on's.

To overcome the drawbacks of IGRP i.e like slow rate of convergence, hop limitation, no support to VLSM etc and IGRP is the successor of RIP which removes the hurdles caused by RIP routing technique.

We all know that IGRP works or supports many protocols other than IP unlike RIP. The same fashion is employed in EIGRP too. The main drawback which EIGRP has overcome is its support for Variable length Subnet Masking (VLSM).

In EIGRP the communication with the fellow routers takes place through the packets "Hello" and exchanging of the information takes place through the "Update" packets.

One more advantage of having EIGRP is it consists of a topology table which consists of the information of the paths from one router to another (shortest path). The shortest path is calculated using the Diffusing Update Algorithm i.e DUAL.

It queries its neighbouring router for a route and that router in turn queries its neighbouring routers and this information is stored in the topology table.

For example let us consider that we are sending a packet of information from point A to D as shown in the below figure.

Here it consists of two paths i.e (A to D) and (A to B and the B to D).Here in EIGRP using DUAL it tracks the neighbouring routes and selects the best which is short and loop-free. The DUAL will be helpful when many routers are involved.


The features of EIGRP are as follows −

  • Maintain for changeable span subnet masking and Classless Inter-Domain Routing (CIDR).

  • It is used to maintain for weight corresponding on parallel links between sites.

  • It has the capability to use similar verification passwords at different periods.

  • Checking whether a route is available or not periodically, and propagates routing change to neighbouring routers if any changes have occured.

  • Backwards compatibility with the IGRP routing protocols.

Metric calculation

Consider the subsequent network presentation related attribute to calculate the EIGRP metric value.

  • Bandwidth

  • Delay

  • Reliability and

  • Weight

EIGRP Metric = 256*((K1*Bandwidth) + (K2*Bandwidth) / (weight) + K3*Delay)*(K5 / (Reliability + K4)))

We know that the default values of K1 and K3 are set to 1, and K2, K4 and K5 are set to 0.


EIGRP Metric = 256*(Bandwidth + Delay)

Border Gateway Protocol (BGP)

It can be defined as a standardized exterior gateway protocol which is developed to interchange routing information and reachability information between various autonomous systems (AS) on the Internet. It is classified as a path vector protocol as well as a distance-vector routing protocol.

It is used for exchanging routing information.This protocol will connect any interwork of an autonomous system. It works while one network router would get connected with that of the other ones.

Here the network cannot be identified to be the best manually, while it is automatically found to be the best and this best network would send in the data by itself.

This would have all the peering partners which the router would send in the traffic to that of the router which has a close destination of the data.


The characteristics of BGP are as follows −

  • Path information

  • Policy support

  • Runs over TCP


The functionalities of BGP are as follows −

  • Initial peer acquisition and authentication.

  • Sending positive or negative reach-ability information.

  • Checks if peers and network connection between them are functioning correctly.

  • Exchange network reach-ability information with some other BGP system.