BGP Attributes Method

[Steven Williams]

Does anybody have a recommendation on which order to learn BGP attributes? Like what is the most common attribute to the least common? If I wanted to start learning these in a lab environment which path should I take on which attributes to lab first?                 

[Bilal Nawaz]

Hello, When BGP has to decide  between paths, there is an order in which BGP considers the path  attributes. BGP looks at path attributes in this order; and you may want to learn about these in this order?

• Highest weight (Cisco-proprietary BGP value)
• Highest local preference (LOCAL_PREF)
• Prefer locally originated route.
• Shortest AS_PATH is preferred.
• Choose  route with lowest origin code. Internal paths are preferred over  external paths, and external paths are preferred over paths with an  origin of "incomplete".
• Lowest multi-exit discriminator (MED)
• External BGP routes preferred over Internal BGP routes.
• If no external route, select path with lowest IGP cost to the next-hop router for iBGP.
• Choose most recent route.
• Choose lowest BGP RID (Router ID).

More info here: http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

Hope this helps

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