From: ying chang (ying_c@xxxxxxxxxxx)
Date: Sat Apr 06 2002 - 20:16:42 GMT-3
Hi hockito,
Sorry, you are right. Can you explain why I get the following (192.168.1.0)
which is the route from R1:
r3#sib
BGP table version is 5, local router ID is 36.1.1.3
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
*>i26.1.1.0/24 36.1.1.6 0 100 0 i
*> 36.1.1.0/24 0.0.0.0 0 32768 i
* i 36.1.1.6 0 100 0 i
* i192.168.1.0 26.1.1.2 20 100 0 1 i
*> 10.1.1.1 30 0 1 1 1 i
r3#
Thanks,
Chang
>From: "Narvaez, Pablo" <Pablo.Narvaez@getronics.com>
>Reply-To: "Narvaez, Pablo" <Pablo.Narvaez@getronics.com>
>To: "ying chang" <ying_c@hotmail.com>, <Upp_and_Upp@hotmail.com>,
><ccielab@groupstudy.com>
>Subject: RE: BGP MED - again
>Date: Sat, 6 Apr 2002 16:55:11 -0600
>
>ummm isn't as-path compared first that ibgp vs ebgp ?
>
>I'll ommit some attribs checked in between for path selection, but isn't
>like this: (?)
>
>- weight
>- local-pref
>- as-path
>- med
>- ebgp vs ibgp
>
>??
>
>So that would give us as-path comparision before ebgp-igrp, correct?
>
>If you prepend from r2 to r3 thru r6, I think r3 will send that route
>prepended, which cause that r1 selects that route thru r2. This way you'll
>have touched only r2 and r1 will see r1-r2.
>
>Am I right?
>
>hockito
>
>
>
>
>-----Original Message-----
>From: ying chang [mailto:ying_c@hotmail.com]
>Sent: Sabado, 06 de Abril de 2002 04:29 p.m.
>To: Upp_and_Upp@hotmail.com; ccielab@groupstudy.com
>Subject: Re: BGP MED - again
>
>
>Hi Sean,
>
>Thanks. Please check R3's BGP table. My topology is
>
> -----R1(AS1)-----
> | |
> R2 R3
> |----R6---------| (R2, R3, R6 are in AS236)
>
>As you can see MED is comparision is skipped. as-path will not do anything
>for this case, because ebgp route is preferred as we've seen from Peter's
>example - as-path comparision come after ebgp-ibgp comparision.
>
>Thanks,
>Chang
>
>R1: AS1 (ISP router)
>
>interface Loopback0
>ip address 192.168.1.1 255.255.255.0
>!
>interface Ethernet0
>no ip address
>shutdown
>!
>interface Serial0
>ip address 10.1.1.1 255.255.255.0
>encapsulation frame-relay
>no fair-queue
>frame-relay map ip 10.1.1.2 110 broadcast
>frame-relay map ip 10.1.1.3 120 broadcast
>no frame-relay inverse-arp
>!
>router bgp 1
>bgp log-neighbor-changes
>network 192.168.1.0
>neighbor 10.1.1.2 remote-as 236
>neighbor 10.1.1.2 soft-reconfiguration inbound
>neighbor 10.1.1.2 route-map set-med1 out
>neighbor 10.1.1.3 remote-as 236
>neighbor 10.1.1.3 soft-reconfiguration inbound
>neighbor 10.1.1.3 route-map set-med2 out
>!
>!
>route-map set-med2 permit 10
>set metric 30
>set as-path prepend 1 1
>!
>route-map set-med1 permit 10
>set metric 20
>!
>
>R2: (AS236, border router 1 to R1)
>!
>interface Ethernet1
>ip address 26.1.1.2 255.255.255.0
>!
>interface Serial0
>ip address 10.1.1.2 255.255.255.0
>encapsulation frame-relay
>no fair-queue
>frame-relay map ip 10.1.1.1 111 broadcast
>frame-relay map ip 10.1.1.3 111 broadcast
>!
>router ospf 100
>router-id 26.1.1.2
>log-adjacency-changes
>passive-interface default
>no passive-interface Ethernet1
>no passive-interface Serial0
>network 0.0.0.0 255.255.255.255 area 0
>!
>router bgp 236
>bgp router-id 26.1.1.2
>bgp always-compare-med
>bgp log-neighbor-changes
>neighbor 10.1.1.1 remote-as 1
>neighbor 10.1.1.1 soft-reconfiguration inbound
>neighbor 26.1.1.6 remote-as 236
>neighbor 26.1.1.6 next-hop-self
>neighbor 36.1.1.3 remote-as 236
>neighbor 36.1.1.3 next-hop-self
>neighbor 36.1.1.3 soft-reconfiguration inbound
>!
>
>R3: (AS236, border router 2 to R1)
>
>!
>interface Ethernet0
>ip address 36.1.1.3 255.255.255.0
>!
>interface Serial0
>ip address 10.1.1.3 255.255.255.0
>encapsulation frame-relay
>no fair-queue
>frame-relay map ip 10.1.1.1 121 broadcast
>frame-relay map ip 10.1.1.2 121 broadcast
>!
>!
>router ospf 100
>router-id 36.1.1.3
>log-adjacency-changes
>passive-interface default
>no passive-interface Ethernet0
>no passive-interface Serial0
>network 0.0.0.0 255.255.255.255 area 0
>!
>router bgp 236
>bgp always-compare-med
>bgp log-neighbor-changes
>bgp always-compare-med
>network 36.1.1.0 mask 255.255.255.0
>neighbor 10.1.1.1 remote-as 1
>neighbor 10.1.1.1 soft-reconfiguration inbound
>neighbor 26.1.1.2 remote-as 236
>neighbor 26.1.1.2 next-hop-self
>neighbor 26.1.1.2 soft-reconfiguration inbound
>neighbor 36.1.1.6 remote-as 236
>neighbor 36.1.1.6 next-hop-self
>neighbor 36.1.1.6 soft-reconfiguration inbound
>!
>
>(R6: internal router, IBGP to R2 and R3 only)
>!
>interface Ethernet0
>ip address 26.1.1.6 255.255.255.0
>!
>interface Ethernet1
>ip address 36.1.1.6 255.255.255.0
>!
>!
>router ospf 100
>router-id 36.1.1.6
>log-adjacency-changes
>passive-interface default
>no passive-interface Ethernet0
>no passive-interface Ethernet1
>network 0.0.0.0 255.255.255.255 area 0
>!
>router bgp 236
>no synchronization
>bgp router-id 36.1.1.6
>bgp always-compare-med
>bgp log-neighbor-changes
>bgp deterministic-med
>network 26.1.1.0 mask 255.255.255.0
>network 36.1.1.0 mask 255.255.255.0
>neighbor 26.1.1.2 remote-as 236
>neighbor 26.1.1.2 soft-reconfiguration inbound
>neighbor 36.1.1.3 remote-as 236
>neighbor 36.1.1.3 soft-reconfiguration inbound
>!
>-------------------------------------------------------
>BGP tables
>-------------------------------------------------------
>r1#sib
>BGP table version is 25, local router ID is 192.168.1.1
>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
>* 26.1.1.0/24 10.1.1.2 0 236 i
>*> 10.1.1.3 0 236 i
>* 36.1.1.0/24 10.1.1.2 0 236 i
>*> 10.1.1.3 0 0 236 i
>*> 192.168.1.0 0.0.0.0 0 32768 i
>r1#
>termserv#2
>[Resuming connection 2 to r2 ... ]
>
>r2#sib
>BGP table version is 4, local router ID is 26.1.1.2
>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
>*>i26.1.1.0/24 26.1.1.6 0 100 0 i
>*>i36.1.1.0/24 26.1.1.6 0 100 0 i
>* i 36.1.1.3 0 100 0 i
>*> 192.168.1.0 10.1.1.1 20 0 1 i
>* i 36.1.1.3 30 100 0 1 1 1 i
>r2#
>termserv#3
>[Resuming connection 3 to r3 ... ]
>
>r3#sib
>BGP table version is 5, local router ID is 36.1.1.3
>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
>*>i26.1.1.0/24 36.1.1.6 0 100 0 i
>*> 36.1.1.0/24 0.0.0.0 0 32768 i
>* i 36.1.1.6 0 100 0 i
>* i192.168.1.0 26.1.1.2 20 100 0 1 i
>*> 10.1.1.1 30 0 1 1 1 i
>r3#
>termserv#6
>[Resuming connection 6 to r6 ... ]
>
>r6#sib
>BGP table version is 8, local router ID is 36.1.1.6
>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
>*> 26.1.1.0/24 0.0.0.0 0 32768 i
>*> 36.1.1.0/24 0.0.0.0 0 32768 i
>* i 36.1.1.3 0 100 0 i
>*>i192.168.1.0 26.1.1.2 20 100 0 1 i
>* i 36.1.1.3 30 100 0 1 1 1 i
>r6#
>
>
>
> >From: "Sean C." <Upp_and_Upp@hotmail.com>
> >Reply-To: "Sean C." <Upp_and_Upp@hotmail.com>
> >To: "ying chang" <ying_c@hotmail.com>, <ccielab@groupstudy.com>
> >Subject: Re: BGP MED - again
> >Date: Sat, 6 Apr 2002 16:50:54 -0800
> >
> >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
> > > > *********************************************
> > > >
This archive was generated by hypermail 2.1.4 : Thu Jun 13 2002 - 10:57:58 GMT-3