From: Sean C. (Upp_and_Upp@xxxxxxxxxxx)
Date: Sat Apr 06 2002 - 21:50:54 GMT-3
Hi Chang,
Concerning your question of how to manipulate routes so the routes will be
preferred on the R1-R3 link over R2-R3 routes while not being able to change
the configs on R1 and R3 (in other words - you can only work on R3) - add a
route-map on R3 and prepend R3's own AS# to routes being advertised to R2.
Since shorter AS paths are preferred, the routes will all come in on the
R1-R3 route which has a shorter AS path. Plus, you don't have to
manipulate anything on R2 and R1.
Hope this helps,
Sean
----- Original Message -----
From: "ying chang" <ying_c@hotmail.com>
To: <dan_schaw@yahoo.com>; <jgraun@attbi.com>; <pdostal@724.com>;
<ccielab@groupstudy.com>
Sent: Saturday, April 06, 2002 12:47 PM
Subject: RE: BGP MED - again
Well, "bgp always compared Med" would not work help in this case as they
both come from AS1.
There are two web pages are helpful:
http://www.cisco.com/warp/public/459/bgp-med.html
http://www.cisco.com/warp/public/459/37.html
Here's my question, if we stick on the original problem, which is we are
trying to tell AS1 to prefer R1-R3 route instead of R2-R3 route, how can we
do it without changing anything on either R1 or R2? Can it be done? In
simple term, R1 and R2 are proctor's routers, and you have to work on R3 to
make R1 and R2 always prefer R1-R3 route.
Thanks,
Chang
>From: Muhamamd Durrani <dan_schaw@yahoo.com>
>Reply-To: Muhamamd Durrani <dan_schaw@yahoo.com>
>To: Jason <jgraun@attbi.com>, "'Peter Dostal'" <pdostal@724.com>,
>ccielab@groupstudy.com
>Subject: RE: BGP MED
>Date: Fri, 5 Apr 2002 23:00:57 -0800 (PST)
>
>you should use "bgp always compared Med " command to
>force BGP to compare MED for destination from
>Different AS systems . By default BGP donot compare
>MED for same destinations from neighbors from
>different AS.
>
>So R2 must have this command and than verify ur result
>....
>
>Regards,
>Muhammad
>
>
>--- Jason <jgraun@attbi.com> wrote:
> > Well iBGP as an Admin distance of 200 while eBGP has
> > an admin distance
> > of 20
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
> > [mailto:nobody@groupstudy.com] On Behalf Of
> > Peter Dostal
> > Sent: Friday, April 05, 2002 6:58 PM
> > To: ccielab@groupstudy.com
> > Subject: BGP MED
> >
> > I have a problem with BGP path selection process.
> > Based on the BGP path
> > selection process I would say that router R2 should
> > choose iBGP path
> > over
> > eBGP (because of lower MED). Any suggestions?
> > Thanks,
> >
> > Peter
> >
> >
> > R1----FrameRelay----R2
> > | |
> > ------Ethernet-------
> > |
> > R3
> >
> > *********************************************
> > hostname R1
> > !
> > interface FastEthernet1/1
> > ip address 192.168.2.3 255.255.255.0
> > !
> > interface Serial1/0
> > ip address 192.168.1.1 255.255.255.0
> > encapsulation frame-relay
> > no keepalive
> > no fair-queue
> > frame-relay interface-dlci 100
> > !
> > router bgp 2
> > bgp log-neighbor-changes
> > neighbor 192.168.1.2 remote-as 2
> > neighbor 192.168.1.2 next-hop-self
> > neighbor 192.168.2.1 remote-as 1
> > neighbor 192.168.2.1 route-map BGP_MAP in
> > no auto-summary
> > !
> > route-map BGP_MAP permit 10
> > set local-preference 100
> >
> > *********************************************
> > hostname R2
> > !
> > interface FastEthernet0/0
> > ip address 192.168.2.2 255.255.255.0
> > !
> > interface Serial0/0
> > ip address 192.168.1.2 255.255.255.252
> > encapsulation frame-relay
> > no keepalive
> > no fair-queue
> > frame-relay interface-dlci 100
> > !
> > router bgp 2
> > bgp log-neighbor-changes
> > neighbor 192.168.1.1 remote-as 2
> > neighbor 192.168.1.1 next-hop-self
> > neighbor 192.168.2.1 remote-as 1
> > neighbor 192.168.2.1 route-map BGP_MAP in
> > no auto-summary
> > !
> > route-map BGP_MAP permit 10
> > set local-preference 100
> > !
> > *********************************************
> > hostname R3
> > !
> > interface FastEthernet0/1
> > ip address 192.168.2.1 255.255.255.0
> > !
> > interface Loopback0
> > ip address 170.2.1.1 255.255.255.240
> > !
> > router bgp 1
> > bgp log-neighbor-changes
> > network 170.2.1.0 mask 255.255.255.240
> > neighbor 192.168.2.2 remote-as 2
> > neighbor 192.168.2.2 route-map BGP_MAP out
> > neighbor 192.168.2.3 remote-as 2
> > no auto-summary
> > !
> > route-map BGP_MAP permit 10
> > set metric 20
> >
> > *********************************************
> > R1#sh ip bgp
> > BGP table version is 8, local router ID is
> > 172.10.1.1
> > 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
> > *> 170.2.1.0/28 192.168.2.1 0
> > 100 0 1 i
> > * i 192.168.1.2 20
> > 100 0 1 i
> > *********************************************
> > R2#sh ip bgp
> > BGP table version is 8, local router ID is
> > 192.168.2.2
> > 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
> > * i170.2.1.0/28 192.168.1.1 0
> > 100 0 1 i
> > *> 192.168.2.1 20
> > 100 0 1 i
> > *********************************************
> >
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