What is Border Gateway Protocol (BGP)

What is Border Gateway Protocol (BGP)? Explained (Part-1)

Before getting right straight to BGP’s functionality and working, it is essential to understand what exactly BGP is and how does it help the Networking Engineers and enthusiasts.

What is Border Gateway Protocol (BGP)?

BGP (Border Gateway Protocol) is an exchange protocol that routes information throughout Autonomous Systems (AS) on the internet.

In simple words, Border Gateway Protocol (BGP) is the key protocol that runs the internet today.

What is an Autonomous System?

An AS or Autonomous System is an internet protocol that consists of a cluster of routing IP prefixes that work under one or several administrative networks.

In simple words, an Autonomous System is a group of networks managed or controlled under one or more entity. This process proceeds via Autonomous System Number (ASN) that allow the ANs to exchange routing information with other systems on the internet.

Can an Autonomous System be private or public?

Yes. Autonomous System Numbers can be set to private or public depending upon necessity.

Now, the question arises here should be about the relationship between BGP and Autonomous Systems. For that let’s take a look at the definition of BGP Autonomous System:

What is BGP Autonomous System?

Networks within the Autonomous System share routing information with other Autonomous Systems via Border Gateway Protocol (BGP).

How Does Border Gateway Protocol Work?

To establish a perfectly stable network system, we need to have the following three things:

  • Autonomous System Number (ASN) assigned by Regional Internet Registry (RIR)
  • A BGP Router to run the process
  • Peering with an entity

What is an RIR?

Regional Internet Registry (RIR) is an organization that offers public addresses to networks or systems in a region. Presently, the following are the five active RIR’s available around the world:

  • African Network Information Center (AFRINIC)
  • American Registry for Internet Number (ARIN)
  • Asia-Pacific Network Information Centre (APNIC)
  • Latin American and Caribbean Network Information Centre (LACNIC)
  • Réseaux IP Européens Network Coordination Centre (RIPE NCC)

Once the RIR generates the public address spaces, these address spaces are then assigned ASN (Autonomous System Number) that identify the spaces and recognise the origin of the routes.


Did you know that Border Gateway Protocol was first introduced in 1989 as a ‘quick fix’ for the internet? Later, BGP proved to be an ideal protocol for long-distance traffic  (Source).

Why Do We Need a BGP Router?

Normal network routers are unable to determine if the network is reliable or best to send data. This is where Border Gateway Protocol (BGP) comes in – BGP acknowledges all the peers, collects the data and send the data + traffic to the nearest router to the destination. This is possible because the BGP allows all the peers to provide its routing information that is stored in Routing Information Base (RIB).

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