BGP Policy-Based Routing Functions Within an Autonomous System
Border Gateway Protocol mandates that a BGP router can advertise only routes that it uses itself to peers in an AS. This is exactly the way that routing hops function on the Internet. BGP is well suited for the modern Internet because it supports any implemented policy that abides by the current “hop-by-hop” routing mechanism. You cannot change how your peer AS will route your packets. You can affect only the manner in which your packets get to your peer ASs.
When a BGP router stores multiple routes to the same destination network in its routing table, it uses a complex sequence of configurable metrics known as attributes to choose the optimal path. Path attributes fall into one of ...
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