Hi, On Thu, Oct 20, 2011 at 06:05:55PM +0400, Andrey Koklin wrote: > The scheme is a bit more complicated, in fact, something like: > > --- R4-AS2 --- > ClientA---> AS4 R1-AS1--(ibgp)--R2-AS1---> R3-AS3 > --- R5-AS3 --- > > We use the same operator (AS3) to organize 2 independent VPN's > for magistral and regional services. > > The problem here looks that AS3 is present already in the path, > so the prefixes are not advertised into another VPN.
Indeed. Actually, they are usually advertised these days, but
then dropped on *import* by AS3.
You can configure the AS3 router allow incoming paths that already have
AS3 in the path with "neighbor ... allowas-in" - but that will defeat
BGP loop-detection, so be careful with what you're asking for.
> Here AS3 = 21017. And what I see on R2:
>
> spring#sh ip bgp 10.36.72.32
> BGP routing table entry for 10.36.72.32/27, version 505812
> Paths: (1 available, best #1, table Default-IP-Routing-Table)
> Not advertised to any peer
I'm not exactly sure when this behaviour was changed, not doing the
filter on the sending side of an eBGP link - but we've seen it years
ago already.
Your best bet might be "not use AS3 in multiple places".
> spring#sh ip bgp 10.36.72.32
> BGP routing table entry for 10.36.72.32/27, version 506076
> Paths: (1 available, best #1, table Default-IP-Routing-Table)
> Not advertised to any peer
> 20485 30835, (received & used)
> 10.36.2.22 (metric 3072) from 213.129.126.1 (10.36.1.1)
> Origin incomplete, metric 0, localpref 100, valid, internal, best
> Originator: 10.36.1.4, Cluster list: 10.36.1.1
So how's your export policies on that router towards the neighbour
that you should see the prefix on?
gert
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