Lenovo ThinkSystem NE2552E, Инструкция по применению

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© Copyright Lenovo 2018 Chapter 27: Border Gateway Protocol
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Selecting Route Paths in BGP
BGP selects only one path as the best path. It does not rely on metric attributes to
determine the best path. When the same network is learned via more than one BGP
peer, BGP uses its policy for selecting the best route to that network. The BGP
implementation on the NE2552E uses the following criteria to select a path when
the same route is received from multiple peers.
1.
Local fixed and static routes are preferred over learned routes.
2.
With iBGP peers, routes with higher local preference values are selected.
3.
In the case of multiple routes of equal preference, the route with lower AS path
weight is selected.
AS path weight = 128
x
AS path length (number of autonomous systems traversed).
4.
In the case of equal weight and routes learned from peers that reside in the same
AS, the lower metric is selected.
Note:
A route with a metric is preferred over a route without a metric.
5.
The lower cost to the next hop of routes is selected.
6.
In the case of equal cost, the eBGP route is preferred over iBGP.
7.
If all routes have same route type (eBGP or iBGP), the route with the lower router
ID is selected.
When the path is selected, BGP puts the selected path in its routing table and
propagates the path to its neighbors.