BGP Series 6: BGP AS-Path Attribute

BGP AS-Path Attribute:

• This attribute is used to decide the best-path for a certain prefix.

• By default, if a bgp router gets two or more updates for the same prefix, then, it will decide at the best path by simply looking at the AS-path attribute...ie. which of these routes went through the fewest number of AS and whichever route had the lowest number (quantity, not value) of AS-path, that is the best route

BGP Series 5: BGP Neighbor States, Message Types, BGP Table and Verification Commands

BGP Neighbor States:

• Idle: bgp process is not even active. Could be due to bgp being administratively shut (or) no route to neighbor in routing table [most likely]
• Connect: [very rarely seen] bgp is waiting for tcp connection to be completed

BGP Series 4: Intro to BGP, BGP Commands, AS-path, ISP, eBgp Requirements, update-source and multi-hop, iBGP Requirements

BGP Series 4

BGP Intro:

• BGP formed on Port 179.
• BGP rides on top of TCP.
• iBGP or eBGP is automatically decided by bgp based on our asn and the asn mentioned in the neighbor command
• There is a lot of differences between the capabilities and functiona lities offered by both iBGP and eBGP
• RFC 1771 is the RFC for bgp

BGP Series 3: Need for iBGP when we have OSPF

Need of iBGP communication for the routes, when we have the IGP protocols (OSPF, RIP) for internal communication?:

• Scalability:

BGP Series 2: eBGP Setup- Requirements, Blueprint

Now that we have decided to use eBGP in our 3-stage Clos, what other things do we need before we can create a final blueprint of what the network will look like? Let's walk through them one by one:

BGP Series 1: eBGP vs iBGP in Datacenters

Why BGP and iBGP vs eBGP in Datacenter

• One of the main requirements of a Leaf-Spine Topology is a strong IP fabric .ie. we should be able to reach any device from any device via IP address