bgp route selection

MrBr @ GMail mrbr.mail at gmail.com
Tue Apr 8 19:10:44 CEST 2014


You might consider some kind of import filter in order to change
local_preference only forl blackholed prefixes
(following was NOT checked  )

filter blackhole {
   if (bgp.nexthop ~ blackhole ) then {
        bgp_local_pref = 500 ;
        accept;
    }
    accept;
}


On Tue, Apr 8, 2014 at 6:50 PM, Thomas Goldberg <t.goldberg77 at gmail.com>wrote:

> 2014-04-07 18:29 GMT+02:00 Ondrej Zajicek <santiago at crfreenet.org>:
> > Hello
> >
> > That is because only resolvable routes are considered (RFC 4271 9.1.2.1),
> > main reason for that condition is to eliminate routes whose bgp_next_hop
> > cannot be resolved using IGP, it also affects routes whose bgp_next_hop
> > is resolved to a unreachable/blackhole/prohibit route.
> >
> > In your case, it could be fixed by adding higher protocol preference
> > (different attribute than bgp_local_pref, currently 100) to b_rr1.
>
> Unfortunately increasing the preference of the b_rr1 session is not an
> option as from my understanding it would completely eliminate the bgp
> route selection rules (All routes learned via b_rr1 are preferred over
> b_dtag1).
> Is there any other solution for this besides doubling the iBGP
> connections (adding seperate blackhole only sessions with higher
> preference)?
>
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