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Re: BGP Confederation config problem...
Andy McConnell wrote: >Avi Freedman suggested using a +1 metric when leaving each member-AS. >But it doesn't seem to help - perhaps I didn't do it right. >In fact, it doesn't look like the metrics are adjusted more than 1. >... >Setting the MED is the crux of the problem - I can set it "statically", >but the idea is to make the whole confederation dynamic. I want the >confederation to work like a true "internet". (Yes, I'm asking for the >world...) Andy, Perhaps a solution, albeit an ugly solution, to the problem is to use a large route-map that matches and increments the MED for the expected range of MED values. Each router would have a route-map to increment the metric on updates that it sends. On the Cisco this configuration might look something like the following: neighbor a.b.c.d route-map INC-MED out ! route-map INC-MED permit 1 match metric 0 set metric 1 route-map INC-MED permit 2 match metric 1 set metric 2 (etc.) If dorian's remark is true... >This won't work because Cisco's bgp implementation skips over MED >from neighboring sub ASes inside a confederation in its decision >process. ...then instead use a route map to increment the local preference for each route received. You would still probably want to set the MED from the local preference before you export routes so that the external neighbors (in other ASes) of the confederation members choose to send data into the confederation at the point closest to the ultimate destination. -Richard