IGRP Routing Protocol

In a host network, the Interior Gateway Routing Protocol (IGRP) is a proprietary distance vector routing protocol that is used to exchange routing information. Cisco was the one who came up with the idea.

The Interior Gateway Routing Protocol (IGRP) regulates the transfer of routing information among linked routers in the host network or autonomous system. The protocol guarantees that every router’s routing table is kept up to date with the most direct route available. IGRP also helps to minimize routing loops by updating itself in response to changes that occur on the network and by implementing error management.

Characteristics

The following are the characteristics of the IGRP (Interior Gateway Routing Protocol):

1. The Interior Gateway Routing Protocol (IGRP) is a distance-vector routing protocol created by Cisco.
2. In addition to bandwidth, delay (by default), reliability, load, and MTU are all measured in the IGRP protocol.
3. It transmits updates every 90 seconds, with a hold-down time of 280 seconds between each broadcasting session.
4. When network changes occur, triggered updates are utilized to expedite the convergence process.
5. The IGRP router command needs the inclusion of an AS number.
6. For routers to communicate routing information, they must be in the same Associated System Number (AS).
7. The maximum number of hops allowed by IGRP is 255. It has a default value of 100 and is often changed to 50 or less.
8. The IGRP AD value is 100.

Goals of IGRP

The Interior Gateway Routing Protocol (IGRP) has two primary objectives:

1. Its primary function is to provide routing information to all linked routers within its border or inside its autonomous system
2. It will automatically update whenever the network topology changes.

Every 90 seconds, it sends out a notice to its neighbors to inform them of any new modifications.

IGRP Timers

IGRP Timers are a kind of timer that is used in the Internet of Things (IoT).

Every 90 seconds, the Interior Gateway Routing Protocol (IGRP) delivers its routing table to its neighbors. When compared to RIP, which might use excessive bandwidth when sending updates every 30 seconds, IGRP’s default update duration of 90 seconds is a plus. RIP’s default update period of 90 seconds is a disadvantage. After 270 seconds, an invalid timer is used by the Interior Gateway Routing Protocol (IGRP) to classify a route as invalid (three times the update timer). When a route is removed from the routing database, IGRP utilizes a flush timer, similar to the way RIP does. The default flush duration is set to 630 seconds (seven times the update period and more than 10 minutes).

In the event that a network goes down or the metric for the network rises, the route is put in hold down mode. Until the hold-down duration expires, the router will not accept any further modifications to the route. This configuration prevents routing loops from forming in the network. The hold-down timer is set at 280 seconds by default (three times the update timer plus 10 seconds).

Functions

The IGRP performs a variety of functions:

Interior Gateway Routing Protocol (IGRP) was developed by Cisco in response to the restrictions of the Routing Information Protocol (RIP), which manages a maximum hop count of 15 per connection. The Interior Gateway Routing Protocol (IGRP) allows for a maximum hop count of 255. The fundamental two objectives of the IGRP are as follows:

1. Route information should be sent between all linked routers inside its border or autonomous system.
2. Continue to update anytime there is a topological, network, or route change that takes place.

Every 90 seconds, the IGRP broadcasts to its neighbors a notice of any new modifications as well as information about its current condition.

IGRP is responsible for maintaining a routing table with the most optimum route to the corresponding nodes and networks inside the parent network, as determined by the parent network. Given that it is a distance-vector protocol, the IGRP calculates the metric for the shortest route to a certain destination based on a number of different criteria. 

Advantages:

1. The procedure is simple and uncomplicated.
2. It takes into account the latency, bandwidth, reliability, and load of a network connection while calculating the score. Consequently, it is quite accurate when it comes to selecting the most suited approach.
3. The use of composite metrics
4. Configuration is straightforward.
5. When compared to RIP, it has more scalability ( 255 hops, 100 by default)

Disadvantages:

1. The hop count is limited to 15; if a packet has traveled through 15 routers and still has another router to travel to, it will be discarded.
2. Does not support a variable-length subnet mask (VLSM), which means that it sends routing updates based only on a fixed-length subnet mask (FLSM) or routes that fall on classful boundaries. As a result, RIP V1 will not function on a network that has been subnetted beyond the standard /8, /16, and /24 (255.0.0.0, 255.255.255.0) or Class A, B, and C network borders (255.0.0.0, 255.255.255.0).
3. Convergence occurs slowly, particularly on large networks.
4. Doesn’t know how much bandwidth is available on a given connection.
5. Doesn’t allow numerous pathways for the same route
6. Routing updates may use a substantial amount of bandwidth since the whole routing database is delivered whenever the state of a connection changes. Routers are prone to routing loops.