What is Border Gateway Protocol (BGP) and Why BGP is Used?
Border Gateway Protocol (BGP) is one of the most important topic in networking courses. In this blog we will discuss all about BGP in details that will help you to understand the concepts of Border Gateway Protocol.
Table of contents
What is BGP?
A routing protocol called Border Gateway Protocol (BGP) is utilised by routers in various autonomous systems (AS) on the Internet to exchange routing data. A group of interconnected networks that are managed by a single administrative domain, such as a business or organisation, is known as an autonomous system (AS).
The effective routing of traffic over the Internet is made possible through BGP, which is used to exchange routing information between routers in various ASes. BGP is a path vector protocol, which means it chooses the best route to a destination based on the qualities and path information of a route. BGP routers communicate about the routes they are aware of and utilise this data to build a routing table that displays the most direct route to each destination.
The only routing protocol utilised to establish routing between various ASes on the Internet is BGP, which is a standard Internet routing protocol. To exchange routing data between various sites or regions, it is also used in enterprise networks, service provider networks, and data centre networks.
In conclusion, BGP is a routing protocol used on the Internet to transmit routing data between routers in various autonomous systems (AS). In addition to being utilised in enterprise, service provider, and data centre networks, it is used to establish routing between various ASes on the Internet.
How many Types of BGP?
There are two main types of Border Gateway Protocol (BGP) that are used in networks:
- External BGP (EBGP): EBGP is used to exchange routing information between different autonomous systems (ASes) on the Internet. In EBGP, routers in different ASes establish BGP sessions with each other to exchange routing information and establish the best path to a destination.
- Internal BGP (IBGP): IBGP is used to exchange routing information within the same autonomous system (AS). IBGP routers are typically used to propagate routing information between different parts of the same AS, or to provide redundancy within an AS. IBGP routers do not need to be directly connected to each other, they can be connected via other BGP routers.
It’s important to remember that although if the two types of BGP are utilised in various ways, they share a common protocol and perform similarly. The way EBGP and IBGP handle the AS PATH parameter is the major distinction between the two protocols. When a route is learned in EBGP, the AS PATH attribute is updated to include the router’s AS number. To avoid loops, the AS number is not assigned to the AS PATH element in IBGP.
In summary, there are two main types of BGP: External BGP (EBGP) and Internal BGP (IBGP). EBGP is used to exchange routing information between different autonomous systems (ASes) on the Internet, while IBGP is used to exchange routing information within the same autonomous system (AS).
How does BGP works?
Border Gateway Protocol (BGP) is a routing protocol used to exchange routing information between routers in different autonomous systems (ASes) on the Internet. BGP routers establish a session, called a BGP neighbor or peer relationship, with each other to exchange routing information.
When two BGP routers establish a neighbor relationship, they exchange their full routing tables with each other. Each router then uses the information it receives to construct a routing table that shows the best path to each destination. BGP routers use a combination of metrics, such as the shortest AS_PATH, the lowest origin code, and the lowest MED (multi-exit discriminator) to determine the best path to a destination.
BGP routers also exchange information about the reachability of a destination. This is done through the use of routing updates, which are sent to inform other routers about changes to the routing table. These updates can include information about new routes that have become available, or routes that have become unavailable.
The optimum route to a destination is chosen by BGP routers via a technique known as route selection. Route attributes like the AS PATH, the origin code, and the MED are used to determine which route to choose. The optimum path is determined by the router to be the one with the lowest metric.
In summary, BGP routers establish a session, called a BGP neighbor or peer relationship, with each other to exchange routing information. When two BGP routers establish a neighbor relationship, they exchange their full routing tables with each other. Each router then uses the information it receives to construct a routing table that shows the best path to each destination. BGP routers use a process called route selection to determine the best path to a destination, based on the attributes of a route, such as the AS_PATH, the origin code, and the MED.
Where is BGP used?
Border Gateway Protocol (BGP) is used in several types of networks, including:
- Internet Service Providers (ISPs): ISPs use BGP to communicate routing data among several Internet autonomous systems (ASes). This enables effective traffic routing between various networks and geographies.
- Enterprise networks: In industrial networks, BGP is also used to exchange routing data across several sites or regions. This enables effective traffic routing within the same organization’s various departments.
- Data center networks: BGP is used in data center networks to exchange routing information between different parts of the same data center or between different data centers. This allows for efficient routing of traffic and enables features such as load balancing and failover.
- Service Provider networks: BGP is used by Service providers for efficient traffic routing between different networks and to provide redundancy.
- Inter-domain routing: BGP is the routing protocol used between different domains of the internet, it’s the only protocol that can be used to exchange routing information between different autonomous systems(AS).
In summary, BGP is widely used in different types of networks such as Internet Service Providers (ISPs), Enterprise networks, Data center networks, Service Provider networks, and mainly used in inter-domain routing on the internet.
Where you can learn BGP?
There are several ways to learn Border Gateway Protocol (BGP), including:
- Online courses: There are many online courses available that cover BGP, such as offered by Cisco. These courses typically include video lectures, quizzes, and hands-on lab exercises to help you learn the concepts and gain practical experience.
- Books: There are also several books available on BGP, such as “BGP Design and Implementation”. These books provide in-depth explanations of the BGP protocol and its configuration and can be used as a reference guide.
- Training centers: Some training centers also offer BGP training courses. These courses are usually taught by certified instructors and provide hands-on experience with BGP.
- Self-study: You can also learn BGP by studying on your own using the Cisco documentation and other resources available online. This method requires self-discipline, time management, and a willingness to experiment with BGP in a lab environment.
- Labs: Practical experience is crucial to master BGP, you can use software-based routers emulators like GNS3, VIRL, or Eve-NG to set up your own lab and practice different BGP scenarios, you can use the documentation and the knowledge you gained from the previous methods to understand how to configure and troubleshoot BGP on these routers.
It’s important to remember that using a variety of techniques you can learn BGP more effectively. For instance, you may read a book, do practices in lab, can take an online course to enhance your knowledge. You may join live training where you can Implement your learnings and knowledge in labs.