What Is BGP?
BGP (Border Gateway Protocol) is the routing protocol that makes the internet work. It enables different autonomous systems (networks) to exchange routing information and determine the best path for data to travel across the internet. BGP is often called the "postal service of the internet."
How It Works
BGP routers establish peering sessions with neighboring routers and exchange routing tables containing network prefixes and path attributes. Each router selects the best path based on policies, AS path length, and other metrics. When network topology changes, BGP propagates updates to ensure global reachability.
Why It Matters
BGP is critical infrastructure — a single misconfiguration can take large portions of the internet offline. BGP hijacking and route leaks are serious security threats that can redirect traffic through malicious networks. Understanding BGP helps diagnose widespread connectivity issues.
Common Issues
- BGP route leaks exposing internal networks
- BGP hijacking redirecting traffic
- Slow convergence causing temporary outages
- Missing RPKI/ROA validation allowing forged announcements