BGP Concepts in MikroTik

1. BGP (Border Gateway Protocol)

BGP is an exterior gateway protocol used to exchange routing and reachability information between different autonomous systems (AS) on the Internet. It is the protocol that powers the global Internet routing system.

BGP routers exchange routing information in the form of paths to specific network destinations. These paths are evaluated based on various attributes, such as path length, origin type, and community values. BGP is policy-based, meaning network administrators can define rules that influence how traffic is routed.

Imagine BGP as the postal service for the Internet. Each autonomous system (AS) is like a country, and BGP ensures that mail (data packets) is delivered to the correct country by the most efficient route. For instance, if a direct route between two ASes is congested, BGP can redirect traffic through an alternative route, ensuring reliable and efficient data delivery.

2. BGP Attributes

BGP attributes are parameters that influence the selection of the best path for routing traffic. These attributes are attached to BGP routes and are used by routers to make routing decisions. Some of the key BGP attributes include:

• AS_PATH: A sequence of AS numbers that the route has traversed. Shorter AS_PATHs are preferred.
• ORIGIN: Indicates how the route was inserted into BGP. Routes with an ORIGIN of IGP (Interior Gateway Protocol) are preferred over EGP (Exterior Gateway Protocol) and INCOMPLETE.
• LOCAL_PREF: A preference value set by the local AS. Higher LOCAL_PREF values are preferred.
• MULTI_EXIT_DISC (MED): A metric used to influence the selection of the best exit point from an AS. Lower MED values are preferred.

Think of BGP attributes as the criteria used by a travel agent to select the best flight for a trip. The agent considers factors like flight duration (AS_PATH), airline reputation (ORIGIN), loyalty points (LOCAL_PREF), and ticket price (MED) to find the optimal flight. Similarly, BGP routers use these attributes to determine the best path for routing data packets.

Understanding BGP and its attributes is crucial for managing complex network environments. By leveraging BGP, network administrators can ensure efficient, scalable, and reliable routing across both enterprise and global networks.