From: Scott Morris (swm@emanon.com)
Date: Fri Sep 29 2006 - 11:03:42 ART
You could implement a route-map on a per-neighbor basis and use "match
as-path" to perhaps set some limits. A bit more work, but technically
possible.
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPExpert VP - Curriculum Development
IPExpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Narbik Kocharians
Sent: Friday, September 29, 2006 2:30 AM
To: Brian Dennis
Cc: Tony Paterra; Cisco certification
Subject: Re: Limiting the number of AS's in an AS Path...
Tony, this command is configured directly under the "router bgp xxx"
process, therefore, it effects the router globally. I don't think there is a
way to apply the command to a given neighbor.
On 9/28/06, Brian Dennis <bdennis@internetworkexpert.com> wrote:
>
> They will not appear in your BGP table. This means they will not be
> sent to a neighbor or be sent to the routing table.
>
> Router#sho run | include (bgp|max|neighbor) router bgp 100 bgp
> log-neighbor-changes bgp maxas-limit 1 neighbor 54.1.1.254 remote-as
> 54 Router# Router#sho ip bgp BGP table version is 9, local router ID
> is 54.1.1.6 Status codes: s suppressed, d damped, h history, * valid,
> > best, i - internal,
> r RIB-failure, S Stale
> Origin codes: i - IGP, e - EGP, ? - incomplete
>
> Network Next Hop Metric LocPrf Weight Path
> *> 28.119.16.0/24 54.1.1.254 0 54 i
> *> 28.119.17.0/24 54.1.1.254 0 54 i
> *> 114.0.0.0 54.1.1.254 0 0 54 i
> *> 115.0.0.0 54.1.1.254 0 0 54 i
> *> 116.0.0.0 54.1.1.254 0 0 54 i
> *> 117.0.0.0 54.1.1.254 0 0 54 i
> *> 118.0.0.0 54.1.1.254 0 0 54 i
> *> 119.0.0.0 54.1.1.254 0 0 54 i
> Router#
> Router(config)#router bgp 100
> Router(config-router)#no bgp maxas-limit 1 Router(config-router)#^Z
> Router#clear ip bgp * Router# *Sep 29 03:25:41.843: %BGP-5-ADJCHANGE:
> neighbor 54.1.1.254 Down User reset *Sep 29 03:25:43.375:
> %BGP-5-ADJCHANGE: neighbor 54.1.1.254 Up Router# Router#sho ip bgp BGP
> table version is 11, local router ID is 54.1.1.6 Status codes: s
> suppressed, d damped, h history, * valid, > best, i - internal,
> r RIB-failure, S Stale
> Origin codes: i - IGP, e - EGP, ? - incomplete
>
> Network Next Hop Metric LocPrf Weight Path
> *> 28.119.16.0/24 54.1.1.254 0 54 i
> *> 28.119.17.0/24 54.1.1.254 0 54 i
> *> 112.0.0.0 54.1.1.254 0 0 54 50 60 i
> *> 113.0.0.0 54.1.1.254 0 0 54 50 60 i
> *> 114.0.0.0 54.1.1.254 0 0 54 i
> *> 115.0.0.0 54.1.1.254 0 0 54 i
> *> 116.0.0.0 54.1.1.254 0 0 54 i
> *> 117.0.0.0 54.1.1.254 0 0 54 i
> *> 118.0.0.0 54.1.1.254 0 0 54 i
> *> 119.0.0.0 54.1.1.254 0 0 54 i
> Router#
>
> HTH,
>
> Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> bdennis@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Direct: 775-745-6404 (Outside the US and Canada)
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Tony Paterra
> Sent: Thursday, September 28, 2006 8:46 PM
> To: Narbik Kocharians
> Cc: Cisco certification
> Subject: Re: Limiting the number of AS's in an AS Path...
>
> Actually, will this command do anything more than prevent the routes
> from entering the routing table?
>
> For instance... Will I stop them from entering my BGP table and/or
> being passed along to peers?
>
> Also can this functionality be implemented on a per-peer basis or only
> globally across all BGP peers? Seems like globally, but you know what
> happens when you "assume" something.
>
> Thanks,
> Tony
>
> On 9/28/06, Narbik Kocharians <narbikk@gmail.com> wrote:
> >
> >
> > (config-router)#bgp maxas-limit 20
> >
> > This command discards routes that have a number of AS-Path
> > segments
> that
> > exceed the specified value. The range is 1 2000. The default value
> in BGP
> > is 75. This command was introduced in IOS release 12.2.
> >
> >
> > On 9/28/06, Tony Paterra <apaterra@gmail.com> wrote:
> > >
> > > All,
> > > If I wanted to filter out routes coming into a BGP peer to only
> routes
> > > that had an AS Path of less than 10 in length, how would you
> recommend
> > > doing it?
> > >
> > > I am looking at creating some pretty elaborate regexp's like....
> > >
> > > ([0-9]*)?_([0-9]*)? (all the way out to 10 places)
> > >
> > > But I'm thinking that there must be a feature or a more elegant
> > > way
> of
> > > accomplishing this. Any thoughts?
> > >
> > >
> > > As always, thanks in advance....
> > >
> > > --
> > > Tony Paterra
> > > apaterra@gmail.com
> > >
> > >
> >
> ______________________________________________________________________
> _
> > > Subscription information may be found at:
> > > http://www.groupstudy.com/list/CCIELab.html
> > >
> >
> >
> >
> > --
> > Narbik Kocharians
> > CCIE# 12410 (R&S, SP, Security)
> > CCSI# 30832
> > Network Learning, Inc. (CCIE class Instructor) www.ccbootcamp.com
> > (CCIE Training)
>
>
> --
> Tony Paterra
> apaterra@gmail.com
>
> ______________________________________________________________________
> _ Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
> ______________________________________________________________________
> _ Subscription information may be found at:
> http://www.groupstudy.com/list/CCIELab.html
>
-- Narbik Kocharians CCIE# 12410 (R&S, SP, Security) CCSI# 30832 Network Learning, Inc. (CCIE class Instructor) www.ccbootcamp.com (CCIE Training)
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