From the course: CCNP Routing (300-101) Cert Prep: 2 Internet Connectivity
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Path selection - Cisco Routers Tutorial
From the course: CCNP Routing (300-101) Cert Prep: 2 Internet Connectivity
Path selection
- [Instructor] BGP's path selection process is far more involved than a standard IGP. But rather than looking at it as additional complexity, I prefer to see it as additional control opportunities. I'll start by presenting this chart. As routes are learned, if more than one path exists to the same destination subnet, the BGP process will run the routes through this best path algorithm to determine which route to install into the routing table. Step zero is whether the route's next hop is reachable or not. An unreachable next hop via the routing table equals an invalid route. Step one is what the weight of the route is. Weight is a non-transitive attribute, which means it isn't shared among routers. Rather, it's locally significant only. It defaults to zero, and the largest weight wins. This is also user configurable. Step two is which route has the largest local preference? Local preference is a value that is transitive inside of a single ASN. This value is attached to a route and…
Contents
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Cisco BGP details5m 13s
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eBGP commands3m 36s
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eBGP loop4m 2s
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eBGP verify3m 26s
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BGP redistribute routes3m 19s
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iBGP basics2m 6s
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iBGP configuration3m 5s
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iBGP sync3m 24s
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iBGP filtering1m 42s
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Filter configuration5m 36s
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iBGP and eBGP groups1m 55s
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Path selection2m 54s
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Path altering by weight4m 1s
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Prepend to eBGP3m 20s
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Multi-exit discrimination1m 54s
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