From: Vladimir Shchutski (vshchutski@xxxxxxxxx)
Date: Fri Apr 27 2001 - 16:48:17 GMT-3
This is for routes originated inside of AS.
Every router has to select the best path. If all
local preference attributes are equal, a local
router selects itself as the best path for networks
it destributes into BGP via "network" or
"redistribute"
command.
Example:
r1#
router bgp 100
network 10.0.0.0
r2#
router bgp 100
R2' BGP table will have R1' IP address as the next-hop
for the best path.
Now we configure R2 to originate network 10.0.0.0
via "network" or "redistribute" command.
r2#
router bgp 100
network 10.0.0.0
OR
redistribute ....
R2' BGP table will have "0.0.0.0" as the next-hop
for the best path. It means,
1) that R2 will advertise itself as the best path to
other IBGP peers.
2) that R2 will advertise network 10.0.0.0 with metric
0 to EBGP peers.
3) that R1 won't be able to set or change any
attributes for the best path in R2' BGP table.
Regards,
Vladimir
--- Curtis Call <curtiscall@home.com> wrote:
> I have a question about the BGP Path Decision
> Criteria #4:
>
> #4: If all local preference attributes are equal,
> select the path that was
> originated by BGP running on the local router.
>
> Could someone give an example of this? I just can't
> understand when a
> router would even bother selecting a path it was
> advertising itself. Is
> this more of a transit issue? For instance, your
> neighbor gives you a path
> to a certain destination that you are also
> advertising and since BGP only
> advertises the best path you would select the path
> that was being
> advertised by you (assuming weight and pref are
> equal) when you advertise
> your paths to other neighbors.
> **Please
> read:http://www.groupstudy.com/list/posting.html
>
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