IGP Interior Gateway Protocol
One type of routing protocol created especially for usage inside a single autonomous system (AS) is called an Interior Gateway Protocol (IGP). An AS is a group of networks under a single administrative domain, like the internal network of a big business or the network of an Internet service provider (ISP). Finding the best route across the network is the main objective of an IGP.
Purpose of IGPs
An IGP’s principal objective is to identify and distribute the best data packet routes inside its single administrative area, or AS. In order to ensure effective data flow, they allow routers to dynamically alter their internal routing tables in response to network changes. Important roles include:
- Assisting routers in discovering every network that is accessible within an AS and figuring out the most effective paths is known as path determination.
- Reachability: Making certain that all network segments inside the AS may be reached by routers.
- Dynamic Updates: Recalculating pathways as necessary and dynamically updating routing tables in response to network events, such as connection failures or the inclusion of new networks.
- Efficiency: By identifying the best routes, latency can be decreased and total data transfer performance improved.
- Routers inside the same AS can exchange routing information with one another.
Also Read About Advantages And Disadvantages Of IPv4 & IPv4 Packet Structure
Important Features of IGPs
IGPs operate according to a number of essential traits that they all share:
Scope: They only function within a single autonomous system and are restricted to a small geographic area or the network of a single organisation.
Routing Protocol Algorithms: These determine how an IGP choose the optimal way, learns routes, and responds to changes in network topology.
Metrics: In order to identify the best route to a destination, IGPs employ a “metric”. This may depend on variables like as load, delay, bandwidth, or hop count. For example, RIP mainly employs hop count, but IGRP uses a composite statistic that includes bandwidth, latency, dependability, load, and Maximum Transmission Unit (MTU).
Administrative Distance (AD): From 0 (most trustworthy) to 255 (untrusted), this number assigns a trustworthiness rating to routing data. When a router learns several paths to the same location using several routing protocols, it becomes extremely important.
Convergence: Convergence is the process by which all of a network’s routers recognize a change in topology, communicate this knowledge, and recalculate their optimal routes. In order to swiftly adjust to changes in network topology and strive for speedy convergence without routing loops, IGPs are built with speed and responsiveness in mind.
Interior gateway protocol types
There are two primary categories for interior gateway protocols, along with a hybrid category:
Distance-Vector Protocols
- These protocols use a “distance” metric, usually hop count, to find the optimal path.
- They promote routes as a vector of direction and distance (exit interface or next-hop router).
- Routers broadcast their whole routing table to neighbours who are directly connected on a regular basis.
- For determining the optimum course of action, they frequently employ the Bellman-Ford algorithm.
- Routing loops and slower convergence are potential problems for distance-vector protocols.
Link-State Protocols
- These protocols create a comprehensive map of the network architecture and are intended to get beyond distance-vector constraints.
- Only when a change takes place does each router use tiny, triggered updates known as Link-State Advertisements (LSAs) to inform every other router in the AS about the state of its own links. Additionally, they provide complete updates on a regular basis at longer intervals (e.g., every 30 minutes).
- Link-state routers have a thorough understanding of the network because they keep three tables up to date: one for neighbours, one for the complete network topology, and the routing table.
- They determine the shortest path based on a cost metric using algorithms such as Dijkstra’s.
Advanced Distance Vector (Balanced Hybrid) Protocols
These protocols offer superior convergence qualities and operational efficiency by combining the advantages of link-state and distance-vector protocols.
IGP examples Typical instances of IGPs are as follows:
Routing Information Protocol (RIP)
The Routing Information Protocol (RIP) is an earlier distance-vector protocol that has a limit of 15 hops and employs hop count as its only measure. RIPv2 supports Variable Length Subnet Masking (VLSM) and has no class. It is 120 miles away administratively.
Interior Gateway Routing Protocol (IGRP)
In order to enhance RIP, Cisco Systems created the proprietary Interior Gateway Routing Protocol (IGRP) in the middle of the 1980s. IGRP permits up to 255 hops (default 100) and employs a composite metric (bandwidth, latency, dependability, load, and MTU). By default, it sends routing updates every 90 seconds. Since IGRP is classful, VLSM is not supported. 100 is its administrative distance.
Enhanced Interior Gateway Routing Protocol (EIGRP)
A sophisticated distance-vector or balanced-hybrid protocol created by Cisco, Enhanced Interior Gateway Routing Protocol (EIGRP) is renowned for its exceptional convergence characteristics and operational efficiency. It selects the optimal path using the Diffusing Update Algorithm (DUAL), is classless, and supports VLSM. For internal roads, the administrative distance is 90, while for external routes, it is 170.
Open Shortest Path First (OSPF)
One popular non-proprietary link-state routing system that is well-known for its effectiveness is Open Shortest Path First (OSPF). It employs Dijkstra’s algorithm, is classless, and supports VLSM. 110 is its administrative distance.
Intermediate System-to-Intermediate System (IS-IS)
Another link-state hierarchical routing technique that is frequently utilized in bigger networks or service provider networks is Intermediate System-to-Intermediate System (IS-IS). 115 is its administrative distance.
IPv6 Support
Protocols that support IPv6 networks have been updated, such as RIPng for RIP, OSPFv3 for OSPF, and EIGRPv6 for EIGRP.
Also Read About Advantages And Disadvantages Of IPv6, IPv6 Address Types