Border Gateway protocol (BGP)101

💡 **Border Gateway Protocol** (BGP) is a standardized exterior gateway protocol designed to exchange routing and reachability information among autonomous systems (AS) on the Internet.

Border Gateway protocol (BGP101%2044720ad38c2e48fe8a44ac46c6bd406a/Untitled.png)

• protocol used to control how data flows
• make up of a lot of self-managed system called autonomous system (AS)
  • collection of routers/ network controlled by one entity ⇒ like a blackbox
  • each is allocated an autonomous system number (ASN) by IANA. 64512-65534 are private, used by BGP to distinguish network
• BGP operates over a tcp/179, but not automatic, peering is manually configured
• BGP is a path-vector protocol = exchanges the best path to destination between peers. The path is called the ASPATH
• direct connect & dynamic VPN use BGP
• AS PATH prepending: set up the path to be longer than it was (must pass through certain AS PATH) and make that AS system select another desired path