IGRP (Interior Gateway Routing Protocol)

Introduction:

Interior Gateway Routing Protocol (IGRP) is a proprietary distance vector routing protocol used by Cisco routers. IGRP is designed to provide a scalable, stable, and efficient routing protocol for large enterprise networks. It uses a variety of metrics to calculate the best path to a destination network and can support up to 255 hops in a single path. IGRP is an advanced routing protocol that provides a high level of control over routing in a network.

IGRP Metrics:

IGRP uses several metrics to determine the best path to a destination network. These metrics include bandwidth, delay, reliability, load, and MTU (Maximum Transmission Unit). Bandwidth is the amount of data that can be transmitted over a link, delay is the time it takes for a packet to travel from the source to the destination, reliability is the likelihood that a link will remain up and functioning, load is the amount of traffic that is currently on a link, and MTU is the maximum packet size that can be transmitted over a link.

IGRP calculates the best path to a destination network by taking into account the values of these metrics. Each metric is assigned a weight, and the weights are used to calculate a composite metric. The composite metric is then used to determine the best path to a destination network.

IGRP Tables:

IGRP uses two tables to store routing information: the routing table and the topology table. The routing table contains the best paths to all known networks, while the topology table contains information about all networks in the network. The topology table is used to calculate the best path to a destination network.

IGRP Convergence:

IGRP uses a variety of mechanisms to ensure that routing information is up-to-date and accurate. These mechanisms include periodic updates, triggered updates, and holddowns. Periodic updates are sent every 90 seconds and contain information about all known networks. Triggered updates are sent in response to changes in the network topology, and holddowns are used to prevent loops from occurring.

IGRP Limitations:

IGRP is a proprietary protocol and is only supported by Cisco routers. It is also a distance vector protocol, which means that it can take longer for routing information to converge in the network. Additionally, IGRP is limited to a maximum hop count of 255, which can be a problem in very large networks.

Conclusion:

IGRP is an advanced routing protocol that provides a high level of control over routing in a network. It uses a variety of metrics to calculate the best path to a destination network and can support up to 255 hops in a single path. IGRP is designed to provide a scalable, stable, and efficient routing protocol for large enterprise networks. However, it is a proprietary protocol and is only supported by Cisco routers. It is also a distance vector protocol, which means that it can take longer for routing information to converge in the network. Nonetheless, IGRP remains an important routing protocol for Cisco networks.