Border Gateway Protocol, the path-vector protocol that holds the internet together and increasingly runs inside enterprise data centers. Articles tagged BGP cover fundamentals, neighbor states, path attributes, best-path selection, traffic engineering, and Cisco IOS XE configuration.
Nine printable pages of BGP: the neighbor state machine, the 13-step path selection algorithm, the major path attributes side by side, AS-path regex patterns, and the commands to type when an adjacency sticks in OpenSent.
Run OSPF, EIGRP, and BGP across GRE tunnels on Cisco IOS XE. Recursive routing fix, OSPF network types, EIGRP metric tuning, and BGP update-source.
MPLS L3VPN architecture: VRFs, Route Distinguishers, Route Targets, MP-BGP for VPNv4, the two-label stack, PE-CE routing, and the Cisco IOS XE configuration.
MP-BGP (RFC 4760) is what lets a single BGP session carry IPv6, VPNv4, EVPN, and more. The AFI/SAFI model, route distinguishers, and how modern data center fabrics use MP-BGP for everything.
BGP's finite state machine has six states: Idle, Connect, Active, OpenSent, OpenConfirm, Established. What each means, why Active is a problem state, and the diagnostic that maps each stuck state to a real cause.
BGP and OSPF solve different problems and almost always run together in production. The technical differences, when each is the right answer, and the architecture pattern most enterprises end up with.
BGP path attributes are the foundation of every traffic engineering technique: local preference, MED, AS-path prepending, communities. Understand the well-known vs optional attribute matrix before touching policy.
BGP uses just four message types: OPEN, UPDATE, KEEPALIVE, and NOTIFICATION. Understanding the field-level format of each makes debug output and packet captures far more readable for anyone troubleshooting BGP.
eBGP and iBGP look similar at a glance but behave very differently around TTL, next-hop, AS-path, and route advertisement. Treating them as the same protocol gets you in trouble fast; here are the rules.
BGP peering does not auto-discover. Every session is deliberately configured, runs over TCP port 179, and walks a strict finite state machine before a single route flows. The foundation you need before touching BGP config.
Every time you load a webpage, your traffic crosses networks owned by different organizations. BGP, the Border Gateway Protocol, is what stitches 75,000+ autonomous systems into a single working internet. Here is how, and why.
Prefix lists are the preferred BGP filtering tool: faster than ACLs, easier to read, and built for matching networks with specific prefix lengths. Every production BGP deployment needs them on inbound and outbound.