What is IGP Interior Gateway Protocol? Introduction to basic concepts of routing protocols

Explanation of IT Terms

What is IGP (Interior Gateway Protocol)? Introduction to basic concepts of routing protocols

Routing protocols are a fundamental component of computer networks, enabling the exchange of routing information between routers to determine the best path for data packets to reach their destination. One such type of routing protocol is the Interior Gateway Protocol (IGP), which operates within a single autonomous system (AS).

Overview of Routing Protocols

Before diving into IGP, let’s first understand the broader concept of routing protocols. A routing protocol is a set of rules and algorithms that routers use to communicate and exchange information about network destinations. This communication helps routers build their routing tables, which contain information about the available paths and metrics associated with each path.

Routing protocols can be categorized into two types: Interior Gateway Protocols (IGPs) and Exterior Gateway Protocols (EGPs). IGPs are used for routing within an autonomous system, whereas EGPs are used to exchange routing information between different autonomous systems.

Interior Gateway Protocol (IGP)

IGP is a type of routing protocol that facilitates communication and route exchange within a single autonomous system. An autonomous system refers to a collection of routers that are under the same administrative control and use a common routing policy.

There are several popular IGPs that are widely used, including Routing Information Protocol (RIP), Open Shortest Path First (OSPF), and Intermediate System to Intermediate System (IS-IS). These protocols differ in their algorithms, metrics, and capabilities.

IGPs are typically used for small to medium-sized networks, such as local area networks (LANs) within an organization. They are designed to efficiently distribute routing information and maintain updated routing tables within the autonomous system.

Key Concepts in IGP

To understand IGP better, let’s explore some key concepts related to this routing protocol:

1. Metrics: IGPs use metrics to determine the best path for routing packets. Metrics can be based on factors such as bandwidth, delay, reliability, or hop count. Each IGP has its own metric calculations to evaluate the suitability of a path.

2. Route summarization: IGPs allow network administrators to summarize a group of network addresses into a single route advertisement. This helps to reduce the size of routing tables and optimize routing performance.

3. Convergence: Convergence refers to the process by which routers in an autonomous system exchange routing information and update their routing tables to reflect network changes. IGPs strive to achieve fast convergence to minimize disruptions and ensure efficient data transfer.


Interior Gateway Protocols (IGPs) play a crucial role in facilitating routing within an autonomous system. They enable routers to communicate and exchange routing information, leading to the establishment of efficient paths for data packets. Understanding the basic concepts of IGPs, such as metrics, route summarization, and convergence, is essential for network administrators and engineers working with routing protocols.

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