What is BGP?

BGP, standing for Border Gateway Protocol, is an exterior gateway protocol (EGP) designed to exchange routing information between ASes. Unlike interior gateway protocols (IGPs) like OSPF, which operate within individual ASes, BGP focuses on routing traffic between different networks and across the internet as a whole.

How does BGP work?

BGP uses path-vector routing, which means it considers not only the next hop but the entire path to a destination when making routing decisions. This allows for more flexible and dynamic routing than distance-vector protocols, which simply choose the shortest path.

BGP relies on several key concepts:

• AS Numbers: Each AS is assigned a unique identifier (AS number) to facilitate routing across different networks.
• BGP Speakers: Routers participating in BGP are called BGP speakers. They exchange routing information between ASes.
• BGP Neighbors:  BGP speakers establish peering relationships with each other to exchange routing information.
• Routing Policies: Network administrators can define policies to control how BGP selects routes, including preferences for specific paths or ASes.

Benefits of BGP:

• Scalability: BGP is designed to handle the complex topology of the internet and can efficiently route traffic across large networks.
• Policy-based routing: Network administrators have fine-grained control over how BGP selects routes, allowing for optimal traffic flow and security.
• Service Provider Networks: Service providers rely on OSPF to distribute routing information across their backbone networks, ensuring smooth data transmission.
• Flexibility: BGP is designed to adapt to changing network conditions and can quickly reroute traffic around outages or congestion.
• Interoperability: BGP is a standardized protocol, ensuring compatibility between different vendor equipment.

Who uses BGP?

BGP is used by all major internet service providers (ISPs) and large organizations to route traffic across the internet. It is essential for ensuring efficient and reliable data delivery across the global network.

What will you learn here?

This page will provide you with a comprehensive understanding of BGP, including:

• Fundamentals: Learn the core concepts of BGP, including its routing policies, path selection, and message types.
• Configuration: Discover how to configure BGP on routers from different vendors.
• Advanced features: Explore advanced BGP features like route filtering, communities, and multihoming.
• Troubleshooting: Learn how to identify and resolve common BGP issues.
• Best practices: Find valuable tips and best practices for implementing BGP effectively in your network.

We encourage you to explore the resources listed below for further learning and to leave any questions or comments you may have.

Resources

• RFC 4271: Border Gateway Protocol (BGP) 4
• BGP Working Group: https://datatracker.ietf.org/wg/
• Cisco BGP documentations:https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book.html
• Juniper BGP documentation: https://www.juniper.net/documentation/us/en/software/junos/bgp/topics/task/routing-protocol-bgp-security-configuring.html

We hope this page serves as a valuable resource on your journey into the world of BGP!