Hi, On Tue, May 31, 2011 at 10:10:14AM -0500, Pete Templin wrote: > Having "learned" in a multi-pop environment, I learned to separate into > three groupings: "edge" routers for upstream transit/peer connections, > "distribution" for downstream customer connections, and "core" as the > glue that holds everything together.
Yeah, I agree. Right now, this doesn't make sense in our network setup
(and the extra routers cost money :) ) but in general, yes.
> Lots of little reasons why:
>
> If another city's WAN link comes into CR1 and you have an uplink there,
> that city's outbound traffic will want to leave via the uplink there
> unless you really motivate BGP to punt the traffic to CR2. In other
> words, if BGP doesn't make a decision before step 9 (Prefer the external
> BGP path over the internal BGP path), all of your traffic arriving on
> CR1 is leaving by CR1's upstream(s).
We do mostly "hot-potato" routing, that is: if local-pref, path-length
and med are all the same, just send out the nearest upstream / peering
point.
Which would do the right thing in that case :-) - but if your policy
is different, it won't.
gert
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