From: Song Mu (songmu@yahoo.com)
Date: Wed Sep 25 2002 - 00:10:09 GMT-3
I am not sure the behaviors. I have tried to use route-maps none of
them works. only the 'bgp default local-pref' works. Do I missed
something?
neighbor 150.50.19.2 route-map bbbb in ------------> to R3
neighbor 10.20.20.20 route-map bbbb in ------------> to R1
neighbor 10.20.20.20 route-map aaaa out ------------> to R1
neighbor 150.50.19.2 route-map aaaa out ------------> to R3
All the above shows:
R3#sh ip bgp
Network Next Hop Metric LocPrf Weight Path
*>i10.20.20.0/24 150.50.19.1 0 100 0 i
*> 10.100.100.0/24 10.30.30.30 0 0 1 i-->R1
* i 10.20.20.20 0 300 0 1 i-->R2
!
access-list 99 permit 10.100.100.0 0.0.0.255
route-map aaaa permit 10
match ip address 99
set local-preference 300
route-map bbbb permit 10
match ip address 99
set local-preference 300
--- stephen.paynter@bt.com wrote:
> Song, I would alter the local-pref on r2 as this will announce it the
> whole
> of AS2. As Brian states have a look on CCO
>
> Stephen Paynter CCIE#10206
> Customer Engineer
> BT Ignite- Customer Engineering Unit, National Solutions
> T: +44 (0)1422 338881 F: +44 (0)1422 316637 M: +44 (0)7974 087949
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> -----Original Message-----
> From: Song Mu [mailto:songmu@yahoo.com]
> Sent: 23 September 2002 21:06
> To: Hongbing Qin; brian@cyscoexpert.com; ccielab@groupstudy.com
> Subject: RE: BGP Challenge
>
>
> I tried to use different ways to accomplish this, but none of them
> seems working. These including change the local pref, metric, change
> ibgp to ebgp, and distance. For some reasons, I have confused myself
> because I can not get the best path from R2 even I shoutdown the
> connection between R1 and R3.
>
> Any ideas?
>
> Song
> --- Hongbing Qin <hqin@houston.sns.slb.com> wrote:
> > Brian,
> >
> > When I reviewed this thread again, I find I still cannot figure out
> > the
> > solution if we exactly follow the original requirement.
> >
> > 1, Weight is not an option, because it should be configured on R3,
> > not on R2.
> >
> > 2. Local preference is not an option, because you are not allowed
> to
> > touch
> > R3, and it's not possible to send Local Preference out.
> >
> > 3. AS-Path is not an option, because it should be configured on
> R1's
> > neighbor to R3.
> >
> > 4. Origin code is not an option, because the route is already
> there.
> >
> > 5. MED is no an option because R3 get the route from R1 without
> > Metric
> > (NULL), so it's impossible for R2 to send lower metric to R3.
> >
> > 6. Obviously, R3 ebgp with R1, and ibgp with R2.
> >
> > Am I right here? Please correct me if I am wrong. Any help? Thanks.
> >
> > Best Regards,
> >
> > Hongbing Qin
> >
> > At 11:32 AM 8/25/2002 -0700, you wrote:
> > >Thai,
> > >
> > > The BGP decision process is:
> > >
> > >Weight
> > >Local-Preference/locally originated
> > >AS-Path
> > >Origin code
> > >MED
> > >EBGP over iBGP
> > >Shortest internal path
> > >Router-ID (lowest)
> > >
> > > Based on this decision process, the reason R3 is routing
> > towards
> > >R1 is the AS-PATH. Distance doesn't come into play until you try
> to
> > >install the route in the routing table. BGP best-path selection
> > >determines which path is best in the BGP table, not which appears
> in
> > the
> > >IP routing table.
> > >
> > > Based on this, it should be fairly obvious which
> attribute
> > you
> > >need to modify (I hope). If not, review Halabi's book or Doyle
> vol
> > 2 to
> > >see how these attributes function.
> > >
> > > For more info on BGP bestpath:
> > >
> > >http://www.cisco.com/warp/public/459/25.shtml
> > >
> > >
> > >HTH
> > >
> > >Brian McGahan, CCIE #8593
> > >Director of Design and Implementation
> > >brian@cyscoexpert.com
> > >
> > >CyscoExpert Corporation
> > >Internetwork Consulting & Training
> > >http://www.cyscoexpert.com
> > >Voice: 847.674.3392
> > >Fax: 847.674.2625
> > >
> > >
> > > > -----Original Message-----
> > > > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
> > Behalf
> > >Of
> > > > Nguyen, Thai
> > > > Sent: Tuesday, August 20, 2002 6:40 PM
> > > > To: 'ccielab@groupstudy.com'
> > > > Subject: BGP Challenge
> > > >
> > > > Hi all,
> > > >
> > > > I've been working on this little problem for few days but have
> > not
> > >been
> > > > able
> > > > to crack it.
> > > > Can anyone shed light into this please?
> > > >
> > > >
> > > >
> > > > R1============R2
> > > > = =
> > > > = =
> > > > = =
> > > > = =
> > > > ========R3
> > > >
> > > >
> > > > R1 is in AS 1
> > > > R2 and R3 is in AS2
> > > >
> > > >
> > > > R1 is advertsing a subnet eg 1.1.1.0/24. Normally R3 will have
> to
> > path
> > >to
> > > > the network, first via R1 directly and second via R2.
> > > > And the preferred path is via R1 because the administrative
> > distance
> > >of
> > > > the
> > > > route learning from R1 is 20 while the route learned via R2 is
> > 200.
> > > >
> > > > The challenge of the excercise is to configure R2 so that R3
> > would
> > > > prefered
> > > > the route it learned from R2 without additional configuration
> on
> > R3.
> > > >
> > > > regards
> > > >
> > > >
> > > > Regards,
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > > Australia Post is committed to providing our customers with
> > excellent
> > > > service. If we can assist you in any way please either
> telephone
> > 13 13
> > >18
>
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