Exterior Gateway Protocol

Definition of Exterior Gateway Protocol

Exterior Gateway Protocol (EGP) refers to a class of routing protocols used for exchanging network reachability information between different autonomous systems on the internet. These protocols help facilitate communication and navigation between large-scale networks independently managed by various organizations. Border Gateway Protocol (BGP) is the most common EGP utilized today because it effectively manages the vast routing tables involved in large-scale internet operations.


The phonetic pronunciation of the keyword “Exterior Gateway Protocol” is:eks-TEER-ee-er GAYT-way PRO-tuh-kawl

Key Takeaways

  1. Exterior Gateway Protocol (EGP) is designed for exchanging routing information between autonomous systems, allowing them to share reachability and network path details on a larger scale.
  2. EGP operates on top of the Internet Protocol (IP) and uses periodic polling or updates to communicate routing information between routers, ensuring appropriate path selection and routing loop prevention.
  3. While EGP is currently considered obsolete, it played a crucial role in the early days of the internet by laying the foundation for modern routing protocols such as Border Gateway Protocol (BGP) that now handle inter-domain communication.

Importance of Exterior Gateway Protocol

The term Exterior Gateway Protocol (EGP) is important in technology because it plays a crucial role in the exchange of routing information between different autonomous systems on the internet.

EGP is designed to connect large networks operated by separate entities such as Internet Service Providers (ISPs) and large enterprises, facilitating communication and ensuring seamless data transfer between these networks.

As part of the overall routing process, EGP aids in handling traffic flow, fault tolerance, and load balancing on the global internet infrastructure.

By providing a standardized method of sharing routing information, it enables routers to make informed decisions about the best path for data packets to travel, ultimately leading to an efficient and reliable internet experience for end-users.


Exterior Gateway Protocol (EGP) plays a crucial role in maintaining the flow of information through the internet, particularly when navigating the interconnection of different autonomous systems (ASes). The main purpose of an EGP is to facilitate efficient and accurate data transmission between ASes, which often comprise distinct networks, domains, or organizations with their own unique routing parameters and policies.

As a specialized type of routing protocol, EGP acts as a communicator between separate ASes, allowing them to exchange routing data that can optimize the routes taken by internet traffic, seamlessly maneuvering through highly complex and disparate networks.

Moreover, the implementation of EGP serves to improve the overall performance and reliability of the internet, as well as to ensure that the information is routed appropriately, adhering to the policies set by the various ASes.

Among various exterior gateway protocols, the Border Gateway Protocol (BGP) stands out as the most widely deployed one, ensuring that required route adjustments are made promptly.

By actively analyzing the best available routes while taking into account important factors such as path selection, shortest paths, and policy enforcement, EGP technology ensures the efficient and resilient flow of data within global networks, thereby laying the foundation for our interconnected world.

Examples of Exterior Gateway Protocol

Exterior Gateway Protocol (EGP) is a routing protocol used to exchange routing information between routers in different autonomous systems (AS). Here are three real-world examples that illustrate EGP’s role in the world of networking.

Border Gateway Protocol (BGP): BGP is arguably the most important and widely adopted EGP in the world today. The entire internet relies on BGP to route traffic between different Autonomous Systems (ASes), which are groups of routers operated by different organizations like Internet Service Providers (ISPs), universities, and large enterprises. BGP allows routers to select the most efficient and stable paths for data traffic, ensuring its proper delivery to the intended destination.

Outsourcing Internet Services: Many organizations choose to outsource their internet connection services to ISPs, which are separate entities operating within their own autonomous systems. In these cases, the organization and the ISP need to use an EGP protocol, like BGP, to exchange routing information between their networks. By doing this, both entities can identify the most optimal routes and direct data packets accordingly.

Multihomed Networks: In some scenarios, an organization may decide to rely on multiple ISPs to provide redundancy and fault tolerance for their internet connectivity. This is referred to as multihoming. Multihomed networks necessitate the use of an EGP like BGP to exchange routing information with multiple autonomous systems. This ensures that all traffic will still be routed efficiently and ensures network resilience, even in the event of a failure or outage within one of the ISPs.

Exterior Gateway Protocol FAQ

1. What is Exterior Gateway Protocol (EGP)?

Exterior Gateway Protocol (EGP) is a class of protocols used by routers to exchange routing information between different autonomous systems on the Internet. EGP is responsible for maintaining connectivity among a group of connected networks and managing how data packets move between them.

2. What is the difference between Exterior Gateway Protocol and Interior Gateway Protocol?

Exterior Gateway Protocols (EGPs) are designed for communication between different autonomous systems, whereas Interior Gateway Protocols (IGPs) handle routing within a single autonomous system. IGPs focus on efficiently routing within a single network, while EGPs ensure accurate and efficient communication among various networks.

3. What are the key features of Exterior Gateway Protocol?

Key features of Exterior Gateway Protocol include:

  • Interaction between autonomous systems
  • Policy-based routing
  • Support for multiple routing metrics
  • Loop prevention mechanisms
  • Hierarchical network organization

4. What are some examples of Exterior Gateway Protocols?

Some common examples of Exterior Gateway Protocols include:

  • Border Gateway Protocol (BGP)
  • Exterior Gateway Protocol (EGP – the original protocol)
  • Intermediate System to Intermediate System (IS-IS)

5. How does Exterior Gateway Protocol affect network performance?

Exterior Gateway Protocols play a critical role in maintaining the scalability and stability of the global Internet by managing the interconnection of autonomous systems. Improper configuration of EGP can lead to routing loops, incorrect paths, or even the complete isolation of an autonomous system. Therefore, it’s crucial to properly configure and manage EGPs to ensure optimal network performance.

Related Technology Terms

  • Border Gateway Protocol (BGP)
  • Routing Information Protocol (RIP)
  • Autonomous Systems (AS)
  • Route Redistribution
  • Path Vector Protocol

Sources for More Information

  • Wikipedia:
  • Cisco:
  • GeeksforGeeks:
  • ScienceDirect:

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