Introduction to BGP

BGP- Border Gateway Protocol

• BGP is Path vector Routing Protocol.
• BGP is the only Exterior Gateway Protocol as of now.
• BGP helps to Route between the Autonomous System's(AS).
• IGP's(RIP, EIGRP, OSPF) are not scalable in the Internet.
• All Interior Gateway protocols (RIP, EIGRP, OSPF) needs to reach the
  destination with the shortest path, But its not in the case of Internet.
• In the Internet, Manipulation of traffic is important rather than shortest path.
• This Traffic Manipulation is done by BGP Attributes, which we will discuss in
  the upcoming sessions.
• BGP is of two Types :
• EBGP  (External-BGP) - AD(20)
• IBGP (Internal BGP) - AD(200)
• EBGP - Communicate with different AS.
• IBGP - Communicate with Same AS.

Why do we need BGP ?

• BGP will not be needed in case of Single ISP.
• BGP is not mandatory in case of Dual ISP. It can be done with the help of Static
  routes also.
• BGP is mainly needed incase Bandwidth Sharing when you have Multiple-ISP's, How
  traffic enters your AS.

Consider this below Scenario, CE-Router is connected to two different ISP. Customer needs to reach
the DNS-SERVER(4.4.4.4) through AS3, and all other Networks need to be reached through the AS2.

If this is the Case BGP can be used.

Consider the above Scenario, If we want what ever the routes that are leaving AS1 will
have go via R3, then in that case BGP can be used. Even the traffic from R2
will leave the AS1 through R2.

 

That's it about Introduction to BGP,

You can also look into my video Tutorial:

If you have any Queries, Just give a comment....