Meaning of "show protocols" output
Does anyone know what "preferred" in the context of rs6-l:~> birdc show protocols all R192_y BIRD 1.3.7 ready. name proto table state since info R192_y BGP Txxxxx up 2013-01-15 11:19:19 Established Description: xxxxx Preference: 100 Input filter: (unnamed) Output filter: (unnamed) Import limit: 150000 Action: restart Routes: 14303 imported, 59164 exported, 22150 preferred means. R192_y is a BGP IPv4 neighbour. TIA, Arnold -- Arnold Nipper / nIPper consulting, Sandhausen, Germany email: arnold@nipper.de phone: +49 6224 5593407 2 mobile: +49 172 2650958 fax: +49 6224 5593407 9
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. -- Elen sila lumenn' omentielvo Ondrej 'SanTiago' Zajicek (email: santiago@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."
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 and the bigger the difference the more often a route shows up as best in other tables resp. the more routes show up as best in other table(s) TIA Arnold -- Arnold Nipper / nIPper consulting, Sandhausen, Germany email: arnold@nipper.de phone: +49 6224 5593407 2 mobile: +49 172 2650958 fax: +49 6224 5593407 9
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@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."
participants (2)
-
Arnold Nipper -
Ondrej Zajicek