BGP - Leaking more specific routes

When implementing BGP there are various ways if influencing incoming traffic. One of those ways is to leak more specific routes to your BGP peers.

Leaking more specific routes can significantly influence incoming traffic due to the way BGP makes routing decisions.

  1. BGP Preference for More Specific Routes: BGP prefers more specific routes over less specific ones. For example, a route to 192.0.2.0/24 (a more specific route) will be preferred over a route to 192.0.2.0/23 (a less specific route) if both are available.
  2. Traffic Attraction: By announcing a more specific route, an AS can attract traffic that was originally destined for a larger network block. This is because other ASes in the Internet will update their routing tables to prefer the more specific path for the subset of the IP range.
  3. Potential for Traffic Hijacking: Maliciously leaking more specific routes can lead to traffic hijacking. An AS could announce a route to an IP block that it does not own, thereby redirecting traffic meant for that IP block through its network.
  4. Load Balancing and Traffic Engineering: Legitimately, ASes may leak more specific routes to influence traffic for purposes like load balancing or traffic engineering. By controlling how traffic enters their network, they can manage bandwidth and performance more effectively.
  5. Increased Routing Table Size: Leaking more specific routes can lead to an increase in the size of global BGP routing tables. This can have performance implications on routers across the Internet, especially those with limited memory and processing power.
  6. Unintended Consequences: Sometimes, more specific routes are leaked unintentionally, which can lead to unexpected traffic patterns, potential network congestion, or even outages if the AS is not equipped to handle the additional traffic load.

Leaking more specific routes in BGP can be used as a tool for traffic management, but it must be done with caution due to its potential impact on traffic patterns and the broader Internet routing ecosystem. Here are examples for BGP route leaking.

Links:

https://forum.networklessons.com/t/leaking-specific-bgp-routes/41122/2?u=lagapidis

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