From the course: Cisco CCNP ENARSI v1.1 (300-410) Cert Prep: 2 VPN Technologies

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BGP path selection

BGP path selection

From the course: Cisco CCNP ENARSI v1.1 (300-410) Cert Prep: 2 VPN Technologies

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BGP path selection

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- [Narrator] We've previously discussed the fact that BGP Route Advertisements consist of Network Layer Reachability Information, or NLRI, and also various path attributes, or PAs. and also various path attributes, or PAs. So here, in order to understand how BGP path selection works, we want to expand upon those path attributes, and actually, there are so many attributes that they're broken down into four distinct categories. Let's start with the first category, which is what we call, well-known mandatory attributes. These attributes must be presented in all BGP updates, or the update will be ignored and considered invalid. So we have listed here: ORIGIN, AS_PATH, and NEXT_HOP. ORIGIN indicates how BGP learned about a particular network. AS_PATH is essentially a list of all the autonomous systems through which the update message has passed, and NEXT_HOP identifies the next-hop IP address that will be used to reach a certain destination. The next category is well-known discretionary…

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