Meaning of "show protocols" output

[Ondrej Zajicek]

On Wed, Feb 06, 2013 at 10:42:38PM +0100, Arnold Nipper wrote:
> On 04.02.2013 11:21, Ondrej Zajicek wrote:
> > On Tue, Jan 29, 2013 at 06:09:04PM +0100, Arnold Nipper wrote:
> >> Does anyone know what "preferred" in the context of
> > 
> > Number of imported routes that are chosen in routing tables as best.
> > 
> > Note that contrary to 'imported' counter, in 'preferred' counter a
> > route is counted once for each routing table where it is best.
> > 
> 
> Understand ...
> 
> Q: what is this information useful for? Clearly imported <= preferred

That is not true - if you receive two routes for the same network from
different BGPs/protocols (in one table), the just one is selected as
best/preferred and propagated further. For the other, the preferred
counter is not increased. So if you have BGP session that has zero
preferred counter (and non-zero imported counter) you could shut it down
and know that it does not change your routing (unless you use
'deterministic med' option, where removing non-best route could cause
changing the best route, but that is some completely different issue).

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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