From: Leo Lin (linyileo@gmail.com)
Date: Fri Apr 20 2007 - 13:32:02 ART
I think it wouldn!/t work, because specifics must be best(which in
Adj-RIBs-Out table), and then you can summary it. So, if you don!/t need
install the summary route decided by specifics, you can block the specifics
inbound, write a static route, and network it, block the network route back
to the original as or set no-export.
Leo
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JU<~HK: alex.arseniev@gmail.com; geert.nijs@simac.be
3-KM: ccielab@groupstudy.com
VwLb: Re: BGP and summary problem
If you don't want the specifics installed in the routing table you could
alsways set the next-hop to those specifics to a next hop that the router
doesn't have or depending on the situation use the 'neighbor x.x.x.x
next-hop unchanged' command.
rr
>From: "Alex Arseniev" <alex.arseniev@gmail.com>
>Reply-To: "Alex Arseniev" <alex.arseniev@gmail.com>
>To: "Geert Nijs" <geert.nijs@simac.be>
>CC: ccielab@groupstudy.com
>Subject: Re: BGP and summary problem
>Date: Fri, 20 Apr 2007 16:13:15 +0100
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>
>Use BGP "table-map" feature?
>http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_command_ref
erence_chapter09186a00801dbab2.html#wp1117257
>Haven't tried this myself, sorry :-(
>Rgds
>Alex
>
>
>On 20/04/07, Geert Nijs <geert.nijs@simac.be> wrote:
> >
> > Hi group,
> >
> > I am having a bit of a problem with the following challenge:
> >
> > Suppose you have a router with a BGP connection. Over this BGP
>connection
> > the following prefixes are received:
> >
> > 192.168.2.0 / 24
> > 192.168.3.0 / 24
> > 192.168.4.0 / 24
> >
> >
> > For some specific ranges, i do not want the very specific prefixes, but
>i
> > only want a summary to be installed into the routing table.
> >
> > For example: i would like to summarize the above prefixes into
>192.168.0.0/ 16 and i only want
> > 192.168.0.0 / 16 in my routing table.
> >
> > Generating the summary is not difficult:
> >
> > router bgp 6500
> > aggregate-address 192.168.0.0 255.255.0.0 summary-only
> >
> > This generates the summary and supresses (in BGP !!) the specific
>prefixes
> > (for outbound BGP advertisements)
> >
> > sh ip bgp
> >
> > *> 192.168.0.0/16
> > s> 192.168.2.0
> > s> 192.168.3.0
> > s> 192.168.4.0
> >
> >
> > However, in the routing table, all prefixes are still installed:
> >
> > 192.168.0.0 / 16
> > 192.168.2.0 / 24
> > 192.168.3.0 / 24
> > 192.168.4.0 / 24
> >
> > I could filter the 192.168.x.0 / 24 prefixes inbound on the BGP session,
> > so that they do not get to the BGP table,
> > but this would prevent the summary from being generated, because there
>is
> > not at least one specific route. Sort of a chicken and egg problem:
> > i don't want the specific prefixes in my routing table, but i can't
>filter
> > them off otherwise the summary isn't generated any more.......
> >
> > Is there a way to prevent the specific routes from being installed into
> > the routing table, however, still generating the summary.....
> >
> > regards,
> > Geert
> >
> > _______________________________________________________________________
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