BGP Explained in detail || BGP Overview, Message Types, States || CCNA & CCNP

Summary

This video discusses the Border Gateway Protocol (BGP), covering its key components, features, and advantages. The session explains how BGP neighborship is formed, the basic syntax of BGP configurations, and the different message types involved. The video also highlights BGP’s role as an exterior gateway protocol that routes information between autonomous systems. Key topics include the path vector protocol, loop prevention, and BGP neighbor management. Additionally, the video delves into the states of BGP communication and its message types, including open, keep-alive, update, and notification messages, with an emphasis on maintaining stable and efficient network communication.

Takeaways

• 😀 BGP (Border Gateway Protocol) is an exterior gateway protocol used for routing information between different autonomous systems (AS).
• 😀 BGP is an open standard protocol, meaning it is available for use by anyone and not limited to specific operating systems.
• 😀 BGP is the slowest routing protocol and uses TCP port 179 for communication.
• 😀 Updates in BGP are incremental and triggered, meaning they only send updates when there are changes to the route (e.g., routes added or deleted).
• 😀 Unlike other routing protocols like OSPF or EIGRP, BGP neighbors must be manually configured and do not use automatic hello packets for discovery.
• 😀 There are two types of BGP: IBGP (Internal BGP) for communication within an AS, and EBGP (External BGP) for communication between different ASes.
• 😀 The administrative distance for EBGP is 20, while for IBGP, it is 200.
• 😀 BGP is a path vector protocol, meaning it includes information about the autonomous systems a route passes through, allowing routers to determine the best path based on AS hops.
• 😀 BGP is a loop-free protocol that prevents routing loops by discarding any route advertisement that contains the router's own AS number.
• 😀 BGP has four types of messages: Open, Keepalive, Update, and Notification. These are used to establish and maintain neighbor relationships and update routing information.
• 😀 The BGP session goes through several states during establishment: Idle, Connect, Active, OpenSent, OpenConfirm, and Established, where the final state means the BGP link is successfully formed.

Q & A

What is an autonomous system in the context of BGP?

An autonomous system (AS) is a group of network devices or a network that is managed and supervised by a single organization or administrative entity. It is a key concept in BGP, as routing between different autonomous systems is a primary function of BGP.

What is the difference between Interior Gateway Protocol (IGP) and Exterior Gateway Protocol (EGP)?

IGP is used to share routing information within a single autonomous system, with examples such as OSPF, EIGRP, and RIP. EGP, on the other hand, is used to share routing information between different autonomous systems, with BGP being the most widely used EGP.

What is BGP and why is it called the 'Internet Protocol'?

BGP (Border Gateway Protocol) is an exterior gateway protocol used to route information between different autonomous systems. It is called the 'Internet Protocol' because it is the primary protocol that facilitates interconnections between service providers, forming the backbone of the Internet.

What is the administrative distance of BGP and how does it differ between iBGP and eBGP?

The administrative distance of BGP is a measure of the trustworthiness of a routing protocol. The administrative distance of eBGP (External BGP) is 20, indicating it is trusted for inter-AS routing, while the administrative distance of iBGP (Internal BGP) is 200, indicating lower trust for routing within an AS.

What are the key advantages of using BGP?

BGP has two main advantages: it is a path vector protocol and it is a loop-free protocol. As a path vector protocol, it shares routing paths with the associated AS numbers, and as a loop-free protocol, it prevents routing loops by discarding routes that include its own AS number.

How does the Path Vector Protocol work in BGP?

In BGP, the Path Vector Protocol works by including the autonomous system numbers (ASNs) in the routing updates. As routers advertise routes to their neighbors, they append their own ASN to the path, helping routers understand the sequence of ASNs required to reach a destination.

How does BGP prevent routing loops?

BGP prevents routing loops by discarding routes that include the router's own ASN in the path. If a router sees its own ASN in a route update, it ignores the update to avoid looping back to itself.

What are the types of BGP messages and their functions?

BGP uses four types of messages: Open, Keepalive, Update, and Notification. The Open message initiates a BGP session, Keepalive maintains the session, Update communicates routing changes, and Notification informs about session termination or errors.

What is the significance of the 'Open' message in BGP?

The 'Open' message in BGP is used to initiate a session between two routers. It contains important information such as the BGP version, AS number, and hold timer. Both routers need to use the same BGP version to establish a connection.

What are the states a BGP session goes through to form a connection?

A BGP session goes through several states: Idle (initial state), Connect (TCP connection initiation), Active (waiting for TCP handshake), OpenSent (sending the Open message), OpenConfirm (waiting for the Open message acknowledgment), and Established (successful session establishment).