Re: BGP AS-PATH PREPEND

Oh I see, so you want to pre-pend everything except that one route, well
that possible, Try then changing the things so as to deny the route you
don't want to pre-pend & permit everything else

!
router bgp 65500
 neighbor 10.255.0.26 route-map AS_CHANGE out
!
route-map AS_CHANGE permit 10
  match ip address prefix OVER_L2
  set as-path prepend 65500 65500 65500
!
ip prefix-list AS_CHANGE deny
ip access-list extended OVER_L2 deny X.X.X..X/XX *!!!the orute you
dont want to prepend*
ip access-list extended OVER_L2 permit 0.0.0.0/0 le 32 *!!!Permit
everything else to get prepended*

Without a full understanding of the topology I have to make some
assumptions & I am trying to understand your issue a bit better,

*1)Because I only want 10.100.60.11 (source) to go over Layer 2 (a name)
10.20.80.11 (destination). The rest should all be prepended. *

*I don't see a route to 10.20.80.11 in the bgp output you send over:*
R1#sh ip bgp
> BGP table version is 196, local router ID is 10.255.255.2
> Status codes: s suppressed, d damped, h history, * valid, > best, i -
> internal,
> r RIB-failure, S Stale, m multipath, b backup-path, x
> best-external, f RT-Filter
> Origin codes: i - IGP, e - EGP, ? - incomplete
> Network Next Hop Metric LocPrf Weight Path
> *> 10.3.0.0/16 0.0.0.0 0 32768 ?
> *> 10.7.0.0/24 0.0.0.0 0 32768 ?
> *> 10.11.0.0/24 0.0.0.0 0 32768 ?
> *> 10.13.0.0/16 10.255.255.1 0 1 65501 ?
> * 10.255.0.26 0 0 65501 65501
65501 65501 ?
> *> 10.16.0.0/24 0.0.0.0 0 32768 ?
> *> 10.20.0.0/24 10.255.255.1 0 1 65501 ?
> * 10.255.0.26 28416 0 65501 65501 65501 65501 ?

\Sam

On Wed, Jan 8, 2014 at 4:53 PM, Cisco Fanatic <ebay_products_at_hotmail.com>wrote:

> Because I only want 10.100.60.11 (source) to go over Layer 2 (a name)
> 10.20.80.11 (destination). The rest should all be prepended.
>
> ip access-list extended OVER_L2
> permit ip host 10.100.60.11 host 10.20.80.11
>
> With your suggestion all the traffic will be prepended (longer AS path)
> and it will not be the best route.
>
>
> ------------------------------
> Date: Wed, 8 Jan 2014 16:36:40 +0000
>
> Subject: Re: BGP AS-PATH PREPEND
> From: sammybibs_at_gmail.com
> To: ebay_products_at_hotmail.com
> CC: mothafungla_at_gmail.com; ccielab_at_groupstudy.com
>
>
> I'm pretty sure the route map is wrong here,
>
> *!!!Yours*
> !
> *!You match the ACL but don't do anything with it.*
> !
> route-map AS_CHANGE permit 10
> match ip address OVER_L2
> !
> *! You then pre-pend everything via the match all in the next statement*
> !
> route-map AS_CHANGE permit 20
> set as-path prepend 65500 65500 65500
> !
>
> *!!!Suggestion*
> !
> !You match the ACL but don't do anything with it.
> !
> route-map AS_CHANGE permit 10
> match ip address OVER_L2
> set as-path prepend 65500 65500 65500
> !
>
> \Sam
>
>
> On Wed, Jan 8, 2014 at 4:31 PM, Cisco Fanatic <ebay_products_at_hotmail.com>wrote:
>
> Sorry, cut-paste issue, too many notepad open.
>
> R1
> ++
>
> !
> router bgp 65500
> neighbor 10.255.0.26 route-map AS_CHANGE out
> !
> route-map AS_CHANGE permit 10
> match ip address OVER_L2
> !
> route-map AS_CHANGE permit 20
> set as-path prepend 65500 65500 65500
> !
> ip access-list extended OVER_L2
> permit ip host 10.100.60.11 host 10.20.80.11
> !
>
> It is still going over the other connection...
>
> R1#traceroute 10.20.80.11
> Type escape sequence to abort.
> Tracing the route to 10.20.80.11
> VRF info: (vrf in name/id, vrf out name/id)
> 1 10.255.255.1 4 msec 0 msec 4 msec
> 2 10.255.255.22 [AS 1] 4 msec 0 msec 4 msec
> 3 10.13.0.253 [AS 65501] 4 msec 4 msec 0 msec
>
>
>
>
>
>
> > Subject: Re: BGP AS-PATH PREPEND
> > From: mothafungla_at_gmail.com
> > Date: Wed, 8 Jan 2014 15:59:21 +0000
> > CC: ccielab_at_groupstudy.com
> > To: ebay_products_at_hotmail.com
> >
> > Where's your match extended ACL in route-map condition ?
> >
> > --
> > BR
> >
> > Tony
> >
> > > On 8 Jan 2014, at 15:47, Cisco Fanatic <ebay_products_at_hotmail.com>
> wrote:
> > >
> > > I understand how AS-PATH PREPEND works, but I am not able to make it
> work
> if I
> > > need to manipulate traffic paths only from a specific source to a
> specific
> > > destination.
> > >
> > > R1
> > > ++
> > >
> > > !
> > > router bgp 65500
> > >
> > > neighbor 10.255.0.26 route-map AS_CHANGE out
> > >
> > > !
> > > route-map AS_CHANGE permit 10
> > >
> > > set as-path prepend 65500 65500 65500
> > >
> > > !
> > >
> > > R2
> > > ++
> > >
> > > !
> > > router bgp 65501
> > >
> > > neighbor 10.255.0.25 route-map AS_CHANGE out
> > >
> > > !
> > > route-map AS_CHANGE permit 10
> > >
> > > set as-path prepend 65501 65501 65501
> > >
> > > !
> > >
> > > R1#sh ip bgp
> > > BGP table version is 196, local router ID is 10.255.255.2
> > > Status codes: s suppressed, d damped, h history, * valid, > best, i -
> > > internal,
> > > r RIB-failure, S Stale, m multipath, b backup-path, x
> > > best-external, f RT-Filter
> > > Origin codes: i - IGP, e - EGP, ? - incomplete
> > > Network Next Hop Metric LocPrf Weight Path
> > > *> 10.3.0.0/16 0.0.0.0 0 32768 ?
> > > *> 10.7.0.0/24 0.0.0.0 0 32768 ?
> > > *> 10.11.0.0/24 0.0.0.0 0 32768 ?
> > > *> 10.13.0.0/16 10.255.255.1 0 1 65501 ?
> > > * 10.255.0.26 0 0 65501
> 65501
> 65501
> > > 65501 ?
> > > *> 10.16.0.0/24 0.0.0.0 0 32768 ?
> > > *> 10.20.0.0/24 10.255.255.1 0 1 65501 ?
> > > * 10.255.0.26 28416 0 65501
> 65501
> 65501
> > > 65501 ?
> > >
> > > I need specific traffic from 10.100.60.11 (Source) to specific
> 10.20.80.11
> > > (Destination) over the 10.255.0.26 connection.
> > >
> > >
> > > 10.100.60.11
> > > _` 10.20.80.11
> > >
> > >
> > > Any thoughts?
> > >
> > >
> > > Blogs and organic groups at http://www.ccie.net
> > >
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Received on Wed Jan 08 2014 - 17:15:06 ART