Re: BGP weight

Because R1 is no longer advertising the other route.

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Marko Milivojevic - CCIE #18427
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On Fri, Nov 19, 2010 at 19:30, Jack Router <pan.router_at_gmail.com> wrote:
> I have a question about BGP weight and how it affects routing on other
> routers. Here is an example:
>
> AS100 B  B  B  B  B AS200
> R1-------------R2
> | B  B  B  B  B  B  B |
> | B  B  B  B  B  B  B |
> | B  B  B  B  B  B  B |
> R4-------------R3
> AS400 B  B  B  B  B AS300
>
> Router R4 advertises network 4.0.0.0
> Rip runs on all routers and advertises links between routers.
>
> R2 sees two paths to 4.0.0.0 :
>
> B Network B  B  B  B  B Next Hop B  B  B  B  B  B Metric LocPrf Weight Path
> * B 4.0.0.0 B  B  B  B  B 10.1.12.1 B  B  B  B  B  B  B  B  B  B  B  B  B  B  B 0 100 400 i
> *> B  B  B  B  B  B  B  B  B 10.1.23.3 B  B  B  B  B  B  B  B  B  B  B  B  B  B  B 0 300 400 i
>
> Now, on router R1 I define weight of 50000 for all routes coming from AS200:
> # neighbor 10.1.12.2 weight 50000
>
> R2 sees now only one route to 4.0.0.0:
> B  Network B  B  B  B  B Next Hop B  B  B  B  B  B Metric LocPrf Weight Path
> *> 4.0.0.0 B  B  B  B  B 10.1.23.3 B  B  B  B  B  B  B  B  B  B  B  B  B  B  B 0 300 400 i
>
> R2 removed path via R1 which is good thing because this would create a loop.
> My question is:
> How R2 knows not to use R1 anymore ?
>
>
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