BGP (Border Gateway Protocol)
The routing protocol that makes the internet work by exchanging routing information between autonomous systems and determining the best paths for data.
What is BGP?
Border Gateway Protocol (BGP) is the routing protocol that underlies the global internet. It enables different networks (autonomous systems) to exchange routing information and make decisions about the best paths for data to travel across the internet.
How BGP Works
BGP routers establish sessions with peers and exchange information about reachable network prefixes. Each BGP router maintains a routing table and applies policies to select the best paths. BGP decisions consider factors like AS path length, origin type, and local preference.
Key Concepts
- Autonomous System (AS): A network under single administrative control
- AS Path: The sequence of AS numbers a route traverses
- BGP Peering: Connections between BGP routers
- Route Announcements: Information about reachable networks
BGP Security Concerns
BGP was designed without built-in security, making it vulnerable to:
- Route hijacking (malicious prefix announcements)
- Route leaks (accidental misconfigurations)
- BGP session hijacking
Modern security measures like RPKI (Resource Public Key Infrastructure) help validate route origins.