From: Daniel Fredrick (dfredrick@gmail.com)
Date: Mon Sep 25 2006 - 10:58:32 ART
Yeah.... I think I am beginning to realize this.
On 9/25/06, Jung-I Lin <easyman.lin@gmail.com> wrote:
>
> Hi,
>
> I've never saw such kind of requirement.
> Even if you enable bgp load balancing on R1 & R6, I believe it still not
> able to have both routes as the best routes.
> Because one route is ebgp(leaned from AS254), the other routes is
> ibgp(from AS3, R5 in this case).
> IMHO I think it is impossible except peering R5 to BB1&BB3 directly.
>
>
> On 9/25/06, Daniel Fredrick <dfredrick@gmail.com > wrote:
> >
> > But if the requirement is to have the routes from BB1 and BB2 in the BGP
> >
> > table in all 3 routers (R1, R5, and R6)... how would this me achieved?
> >
> > On 9/24/06, Ivan <ivan@iip.net> wrote:
> > >
> > > All of the BGP-routers advertise their best path to BGP-peers. In my
> > > understading all condition is equal except AS-path length. As-path
> > length
> > > is
> > > determine condition for path choosing.
> > > To overlay this you can try ignore as-path length and to decide
> > BGP-path
> > > on
> > > router ID or metric.
> > >
> > > bgp bestpath as-path ignore
> > >
> > > On Sunday 24 September 2006 19:51, Daniel Fredrick wrote:
> > > > OK... that makes sense, but is there a way to get all of them to
> > have
> > > two
> > > > routes in the bgp table? Only thing I could think of is that
> > prepending
> > > the
> > > > as on R6.
> > > >
> > > > Thanks,
> > > > Dan
> > > >
> > > > On 9/24/06, Marvin Greenlee < marvingreenlee@yahoo.com> wrote:
> > > > > Is the issue that R5 and R6 are removing them or that
> > > > > R1 isn't advertising them? Debug your BGP updates. I
> > > > > would guess that R1 isn't advertising them to R5,
> > > > > because his best path for the networks is the route
> > > > > learned via R5. R1 is only going to advertise his
> > > > > best path. When the other link drops, R1's best path
> > > > > is via AS254 directly, and he will advertise that to
> > > > > R5 and R6.
> > > > >
> > > > > Thanks,
> > > > > Marvin
> > > > >
> > > > > --- Daniel Fredrick < dfredrick@gmail.com> wrote:
> > > > > > Here's the BGP topology...
> > > > > >
> > > > > > AS254 AS254
> > > > > > (BB1) (BB2)
> > > > > >
> > > > > > | RR |
> > > > > >
> > > > > > (R1)---------(R5)-----------(R6)
> > > > > > AS3 AS3 AS3
> > > > > >
> > > > > > R5 is the route reflector.
> > > > > >
> > > > > > OK... now BB1 and BB2 are sending the same BGP
> > > > > > routes. The only difference
> > > > > > is BB1 is sending the same routes is an aspath of
> > > > > > "254 253". BB2 is sending
> > > > > > the same routes, but with an aspath of just "254"
> > > > > >
> > > > > > OK... so here's my problem. When I do a "show ip
> > > > > > bgp" all of the routers
> > > > > > don't show both routes from BB1 and BB2.
> > > > > >
> > > > > > R1 shows both routes from BB1 and BB2, with BB2
> > > > > > routes preferred... since it
> > > > > > has a shorter BGP path.
> > > > > >
> > > > > > R5 only shows only BB2 routes.
> > > > > >
> > > > > > R6 only shows BB2 routes.
> > > > > >
> > > > > > So... here comes the confusing part...
> > > > > >
> > > > > > When R5 loses R6 as a bgp neighbor and it is down,
> > > > > > the routes from BB2
> > > > > > disappear in "show ip bgp" and the routes from BB1
> > > > > > show up in "show ip bgp"
> > > > > >
> > > > > > So what could cause R5 and R6 to remove the routes
> > > > > > from the bgp table? It
> > > > > > should keep them in there... but just not use them
> > > > > > as a preferred route.
> > > > > >
> > > > > > Thanks,
> > > > > > Dan
> > > > >
> > > > >
> > >
> > _______________________________________________________________________
> > > > >
> > > > > > Subscription information may be found at:
> > > > > > http://www.groupstudy.com/list/CCIELab.html
> > > > >
> > > > > __________________________________________________
> > > > > Do You Yahoo!?
> > > > > Tired of spam? Yahoo! Mail has the best spam protection around
> > > > > http://mail.yahoo.com
> > > >
> > > >
> > _______________________________________________________________________
> > > > Subscription information may be found at:
> > > > http://www.groupstudy.com/list/CCIELab.html
> > >
> > > --
> > > Ivan
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
> >
>
>
>
> --
> Thanks
> Best Regards,
>
> Jung-I Lin
This archive was generated by hypermail 2.1.4 : Sun Oct 01 2006 - 16:55:41 ART