How does BGP work?

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BGP is an exterior gateway protocol designed to facilitate routing between Autonomous Systems (AS), which form the backbone of the internet. In simple terms, each AS receives route information advertised by neighboring ASes and builds its own routing table. BGP determines the best path based on various metrics (such as AS_PATH length, NEXT_HOP, LOCAL_PREFERENCE, etc.). For example, a shorter AS_PATH is preferred because it indicates fewer hops, making data transmission more reliable and faster. In practice, I started learning BGP with Cisco Packet Tracer simulations. Neighbor relationships (neighbors) are established statically between ASes that connect to each other, allowing the exchange of network information from neighboring ASes. The most important feature of BGP is that it has no central control; each AS manages its own decision-making process, creating a large distributed system that prevents the internet from collapsing. My recommendation is that while learning BGP, you should conduct practical experiments using real Cisco Junket routers or BGP simulations on GNS3.