[c-nsp] IBGP route stays stuck

[Pete Lumbis]

Maybe the PE1 eBGP peer is also preferring the route via PE2, so the
announcement to PE1 contains it's own AS Number?

On Thu, Oct 23, 2014 at 11:47 AM, Pasquino Andrea <andrea.pasquino at eng.it>
wrote:

> Pete,
>
> here you are steady state: dummy route 7.7.7.7/32 comes from EBGP
>
> PE1:
>      Network          Next Hop            Metric LocPrf Weight Path
>  *>  7.7.7.7/32       X.X.X.93                    222      0   XXX9 XXX7
> 65000 ?
> PE2:
>    Network            Next Hop            Metric LocPrf Weight Path
>  *>i 7.7.7.7/32       X.X.X.8                0    222      0   XXX9 XXX7
> 65000 ?
>
>
> ip route vrf xxxx 7.7.7.7 255.255.255.255 Dialer319 172.19.9.2 240
> !
> router bgp XXXX
> !
> address-family ipv4 vrf xxxx
>   redistribute static route-map TER
> !
> route-map TER permit 10
>  set local-preference 33
>  set weight 0
>
> +++++++++++++++++++++++++++++++++++++++++++++
>
> Now I stop announcing the route from EBGP, the floating static kicks in:
>
> PE1:
> PSMDCI11ME1#sh ip bgp vpnv4 vrf sumitomo
> *>i 7.7.7.7/32       X.X.X.2                0     33      0 ?
> PE2:
>    Network          Next Hop            Metric LocPrf Weight Path
> *> 7.7.7.7/32       X.X.X.2               0     33      0 ?
>
> +++++++++++++++++++++++++++++++++++++++++++++
>
> When I restart announcing the route from EBGP nothing changes...
> I have to delete the static route on PE2 and putting it back again.
>
> Andrea
>
>
> From: Pete Lumbis [mailto:alumbis at gmail.com]
> Sent: giovedì 23 ottobre 2014 17:15
> To: Pasquino Andrea
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] IBGP route stays stuck
>
> Do you happen to have the output of the BGP tables (specifically the
> a.b.c.d route) from PE1 and PE2 during the failure? My guess is that it's
> "expected" (in the sense BGP is doing what it's supposed to, even if
> undesired) and seeing it in the broken state should make it easy to reverse
> engineer why it happens.
>
> -Pete
>
> On Thu, Oct 23, 2014 at 9:59 AM, Pasquino Andrea <andrea.pasquino at eng.it>
> wrote:
> Pete,
>
> Actually the floating static on PE2 is redistributed  with weight 0 by
> default.
> I have configured on PE2 a route-map in order to redistribute into BGP the
> routes coming from MPBGP with a higher weight, no luck. I think I’m going
> to check with TAC…
>
> Andrea
>
> From: Pete Lumbis [mailto:alumbis at gmail.com]
> Sent: mercoledì 22 ottobre 2014 15:44
> To: Pasquino Andrea
> Cc: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] IBGP route stays stuck
>
> Perhaps when the floating static kicks in on PE2 the weight will be 32768,
> most likely making it the best route in the BGP table, causing it to
> advertise to PE1? I've seen similar configurations run into this. If this
> is your issue the solution is a route-map on the redistribution statement
> setting the weight to 0
>
> On Wed, Oct 22, 2014 at 2:30 AM, Pasquino Andrea <andrea.pasquino at eng.it
> <mailto:andrea.pasquino at eng.it>> wrote:
> Hello,
>
> This is the scenario:
>
> I have PE1 and PE2 in AS100
> PE1 has an EBGP peering with AS200 and receives a certain prefix a.b.c.d
> with LP=222
> The same prefix a.b.c.d is redistributed on PE2 with LP=33 from a floating
> static route, and serves as a back-up route
>
> Now here's what happens: if for some reason AS200 stops announcing prefix
> a.b.c.d, then the announcement from PE2 kicks and we are happy (back-up
> runs fine)
>
> When  AS200 starts again announcing prefix a.b.c.d, then the announcement
> from PE2 does not get flushed from PE1 and PE2. We have to erase the "ip
> route vrf blahblah" command and rewrite it
>
> Have you any clues ?
>
> Andrea
>
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