BGP AS Path

The AS Path is a key BGP attribute that lists the sequence of Autonomous Systems (ASes) a route has traversed to reach a destination. It helps prevent routing loops by ensuring a router rejects routes that include its own AS number in the path. The AS Path is crucial in BGP's decision-making process, with shorter paths generally preferred during route selection.

This attribute can be manipulated using techniques like AS Path prepending, where an AS adds its own number multiple times to make a route less attractive. It also provides visibility into the route’s traversal, aiding in network troubleshooting and policy control. The AS Path consists of ordered (AS_SEQUENCE) or unordered (AS_SET) segments, ensuring accurate and flexible routing across interconnected networks.

Links:

https://networklessons.com/bgp/bgp-attributes-and-path-selection

https://networklessons.com/bgp/how-to-configure-bgp-as-path-prepending