From: balaji.balakrishnan (balaji.balakrishnan@swift.com)
Date: Wed Feb 19 2003 - 17:23:29 GMT-3
Hi Cezar,
I am not sure about this specific problem. But usually this behavior happens when R1 receives 20.20.20.0/24 from R2 and mark it as
best. On that case, since it is already has the best route, it will not send the route 20.20.20.0/24 it received from AS200 to R2 .
Rgds,
Bala.
Cezar Fistik wrote:
> Hi all,
>
> The network is as follows:
>
> AS200 -------- AS400
> \ /
> R1--R2--R3
>
> R1, R2, R3 are all in AS500. R2 is a route reflector. AS400 receives a
> route, let's say to 20.20.20.0/24 from anohter AS (not shown here). AS400
> sends this route to AS500, exactly to R3 and to AS200. AS200 also sends
> this route to SA500, to R1. No synch is configured on all routers in AS500
> and next-hop-self is configuredon R1 and R3. All routers in AS500 know
> about all nets in SA200 and AS400.
>
> Here is the point where something that I cannot understand happens.
>
> R3 sends the route to R2 (RR). R2 sends the route to R1 (RR Client).
> R1 receives the route from AS200 and AFAIK it should send it to R2(its
> route reflector), btu it doesn't. More strange is the fact that R2 and R3
> prefer the path to 20.20.20.0/24 through AS400, but R1 prefers the path
> through 200 400, despite R1 has info about both paths in its BGP table.
>
> I was wondering, why R2 and R3 don't even have the route to 20.20.20.0/24
> through AS200. They only have one route through AS400 drectly.
>
> As I mentioned R1 doesn't send the route to 20.20.20.0/24 that it received
> from AS200 to its internal neighbor, but I tried to shutdown the interface
> between the R2 and R3 and the route to 20.20.20.0/24 immediately appears in
> R2 table
>
> If I change on R2 route selection attributes, making the 20.20.20.0/24 more
> preferable through AS200 then all the routers in AS500 selects this route,
> I mean tht R1 starts sending this route to R2.
>
> In a word, I'm confused and if anybody knows what happens here please be so
> kind and give me an advice.
>
> Thanks,
>
> Cezar Fistik
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