[c-nsp] BGP re-announcement question

[Aaron]

I think you answered your own question.
Your customer is prepending to many times.
Count the # of ASNs.
6 vs 5. If they reduce their prepend by 1, ASN count would be the same,
then we would move to origin, the same, EBGP over iBGP.
So I'd ask them to reduce it by 2.


 27241 27241 27241 27241 27241 27241, (received & used)

    204.8.83.14 (metric 1) from 172.18.18.20 (172.18.18.20)

      Origin IGP, metric 300, localpref 100, valid, internal


  12271 7843 3356 46887 27241, (received & used)

    24.29.112.25 from 24.29.112.25 (69.193.224.79)

      Origin IGP, localpref 100, valid, external, best

      Community: 7843:2161 7843:2303 7843:2313


On Mon, Jul 29, 2013 at 6:53 PM, Adam Greene <maillist at webjogger.net> wrote:

> Hi!
>
>
>
> We are receiving a heavily prepended route announcement from a customer and
> are trying to re-announce it to our upstream provider, without success.
>
>
>
> We learn the route on router A via eBGP. Router A announces the route to
> Router B via iBGP. Router B is then supposed to announce it to Router C,
> our
> upstream provider, via eBGP, but it is not.
>
>
>
> Here is what Router B is seeing:
>
>
>
> 7206VXR#sh ip bgp 198.11.15.0
>
> BGP routing table entry for 198.11.15.0/24, version 262804866
>
> Paths: (2 available, best #2, table Default-IP-Routing-Table)
>
>
>
>   27241 27241 27241 27241 27241 27241, (received & used)
>
>     204.8.83.14 (metric 1) from 172.18.18.20 (172.18.18.20)
>
>       Origin IGP, metric 300, localpref 100, valid, internal
>
>   12271 7843 3356 46887 27241, (received & used)
>
>     24.29.112.25 from 24.29.112.25 (69.193.224.79)
>
>       Origin IGP, localpref 100, valid, external, best
>
>       Community: 7843:2161 7843:2303 7843:2313
>
>
>
> As you can see, the eBGP route Router B is receiving from Router C
> (upstream) is considered the best route. Is that why we are not
> reannouncing
> it back upstream?
>
>
>
> Prefix-lists and route-maps have all been checked, including regular
> expressions; we allow out ^27241(_27241)*$ and a "sh ip bgp regexp
> ^27241(_27241)*$" provides this output:
>
>
>
>    Network          Next Hop            Metric LocPrf Weight Path
>
> * i198.11.15.0      204.8.83.14            300    100      0 27241 27241
> 27241 27241 27241 27241 i
>
>
>
> I do wonder a bit about the "metric 300" (I think my customer might be
> trying to weight things) but I'm not sure that's coming into play here or
> not.
>
>
>
> This was working fine recently, with no changes on our end, but the
> customer
> was announcing without any prepends, and I'm not sure if the origin was "?"
> before, or "i" like it is now.
>
>
>
> Thanks,
>
> Adam
>
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