From: Volkov, Dmitry (Toronto - BCE) (dmitry_volkov@xxxxxxxxx)
Date: Thu Aug 29 2002 - 00:03:36 GMT-3
> -----Original Message-----
> From: Angelo De Guzman [mailto:ghie_pogi@yahoo.com]
> Sent: Wednesday, August 28, 2002 10:23 PM
> To: Khalid Siddiq; Colin Barber; Graham, John; ccielab@groupstudy.com
> Subject: RE: Page 376 of Internet Routing by Halabi
>
>
> Hi To all,
> I was able to solved this problem by putting in
> no-synchronization under my router bgp configuration
> (R10 and R7). Somebody from the list posted that a
> route is not put into the BGP path selection process
> if the route is not synchronized.
Right this is true if Synchronization is enabled (default).
> My config below
> works fine by just adding the no-sync.
Right, because You disabled synchronization (see above)
> always-compare-med won't solved this problem
> because the metric of the route does not come from a
> different AS. As I've read, by default BGP always
> compare the MED when an update for a route comes from
> the same AS.
This is partially true. Please read thread about BGP DETERMINISTIC-MED
and read http://www.cisco.com/warp/customer/459/bgp-med.html
ans http://www.cisco.com/warp/public/459/37.html
> And as an addition to this as I may say,
> you have to have that route synchronized before it is
> put into the bgp path selection process.
Only If You have Sync enabled (which is by default)
do no-sync and forget about syncronization in best path selection process
Cheers,
Dmitry
> Please correct me if I'm wrong...
> Thanks to all,
> Angelo
>
> --- Khalid Siddiq <khalid@sys.net.pk> wrote:
> > Chech the next-hop ip address 192.68.6.1 on R10
> > router, it should be in routing table.
> > khalid
> >
> > -----Original Message-----
> > From: Colin Barber
> > [mailto:Colin.Barber@telewest.co.uk]
> > Sent: Wednesday, August 28, 2002 3:14 PM
> > To: 'Graham, John'; 'ccielab@groupstudy.com'
> > Subject: RE: Page 376 of Internet Routing by Halabi
> >
> >
> > MED is being sent from R5 in AS3 to two routers (R7
> > and R10) in AS1.
> > Therefore the two routes being compared on R7 and
> > R10 have MED values from a
> > single AS.
> >
> > Colin
> > -----Original Message-----
> > From: Graham, John [mailto:john.graham@cgey.com]
> > Sent: 28 August 2002 10:54
> > To: 'Colin Barber'; 'Robert Miller';
> > 'ccielab@groupstudy.com'
> > Subject: RE: Page 376 of Internet Routing by Halabi
> >
> >
> > Isn't he trying to prefer one route to a destination
> > over another on a local
> > basis ?
> >
> > -----Original Message-----
> > From: Colin Barber
> > [mailto:Colin.Barber@telewest.co.uk]
> > Sent: 27 August 2002 14:32
> > To: 'Robert Miller'; 'ccielab@groupstudy.com'
> > Subject: RE: Page 376 of Internet Routing by Halabi
> >
> >
> > You shouldn't need 'always-compare-med' as the route
> > is being advertised by
> > only one AS (AS3)
> >
> > Colin
> > -----Original Message-----
> > From: Robert Miller [mailto:rmiller@absitech.com]
> > Sent: 27 August 2002 14:17
> > To: ccielab@groupstudy.com
> > Subject: RE: Page 376 of Internet Routing by Halabi
> >
> >
> > Refer to the rules for comparing Med for external
> > vs. internal AS's
> >
> > "always-compare-med"
> >
> > Robert
> > ------------------------------------------------
> > On Tue, 27 Aug 2002 05:22:36 -0700 (PDT), Angelo De
> > Guzman
> > <ghie_pogi@yahoo.com> wrote:
> >
> > > Hi to All,
> > >
> > >
> > > R10 ------R7
> > > | /
> > > | /
> > > | /
> > > R5
> > >
> > > R10 and R7 in AS 1.
> > > R5 in AS 3
> > >
> > > My objective is for R10 to prefer the path to
> > R7
> > > going into AS 5. I'm only allowed to change the
> > metric
> > > to make this work. The link between R5 and R10
> > will
> > > only be used when R5 to R7 link fails.
> > >
> > > Here's my Config.
> > >
> > > R5
> > >
> > > router BGP 3
> > > network 172.16.220.0 mask 255.255.255.0
> > > neighbor 172.16.20.1 remote-as 1
> > > neighbor 172.16.20.1 route-map setmetric out
> > > neighbor 192.68.6.2 remote-as 1
> > > neighbor 192.68.6.2 route-map setmetric1 out
> > > no auto-summary
> > >
> > > route-map setmetric permit 10
> > > set metric 100
> > >
> > > route-map setmetric1 permit 10
> > > set metric 50
> > >
> > > These are the sh ip bgp for R7 and R10
> > >
> > > R10#sh ip bgp
> > > BGP table version is 3, local router ID is
> > 192.68.11.1
> > > Status codes: s suppressed, d damped, h history, *
> > > valid, > best, i - internal
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > >
> > > Network Next Hop Metric LocPrf
> > Weight
> > > Path
> > > *> 172.16.220.0/24 172.16.20.2 100 0
> > 3 i
> > > * i 192.68.6.1 50 100 0
> > 3 i
> > > *> 192.68.11.0 0.0.0.0 0 32768
> > i
> > >
> > >
> > > R7#sh ip bgp
> > > BGP table version is 7, local router ID is
> > 192.68.9.2
> > > Status codes: s suppressed, d damped, h history, *
> > > valid, > best, i - internal
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > >
> > > Network Next Hop Metric LocPrf
> > > Weight Path
> > > * i172.16.220.0/24 172.16.20.2 100 100
> > 0 3
> > > i
> > > *> 192.68.9.1 50
> > 0 3
> > > i
> > > *>i192.68.11.0 192.68.6.2 0 100
> > 0 i
> > >
> > > Why does R10 still prefers the link between R10
> > and
> > > R5. Eventhough the network 172.16.220.0/24 has a
> > > metric of 100.
> > > Thanks,
> > > Angelo
> > >
> > >
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:48:41 GMT-3