From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Tue Nov 15 2005 - 04:17:15 GMT-3
Prefix list is still scalable .
Let us take for a discussion ... what does an aggregate with summary-only
does ????
It advertises summary route and suppress all the more specific routes . This
is same as using a prefix list which denies all the more specific routes .
For example .
if you have routes for 192.168.1.0/24 and 192.168.2.0/24 And you will like
to summarize it to 192.168.0.0 /16
Now prefix list should be
ip prefix-list 1 permit 192.168.0.0/16
ip prefix-list 1 deny 192.168.0.0/16 ge 16
This is very much scalable in sense . In the future a route has been added
say 192.168.200.0/24 . Even then solution will be still valid . To summarize
This solution is as scalable as aggregate-address 192.168.0.0 255.255.0.0
summary-only
Thanks and Regards
Arun
----- Original Message -----
From: "Chad Hintz" <ccie_2b2004@yahoo.com>
To: "Paresh Khatri" <Paresh.Khatri@aapt.com.au>; "Daniel Berlinski"
<Daniel.Berlinski@telecom.co.nz>; <ccielab@groupstudy.com>
Sent: Tuesday, November 15, 2005 10:49 AM
Subject: RE: BGP question
> Daniel,
>
> I would create a prefix list permiting only the summary, I know you said
this was not scalable but with sequence numbers it is. Since you need to
add additional routes you can create a seq number higher than the original
(by default is 5).
>
> So for additional routes you only need to create another line in the
prefix for each route. You can also think of it in the other fashion by
using a prefix list to deny the routes from bb3 except the summary and
create a permit 0.0.0.0/0 le 32 line to permit all other traffic.
>
> HTH,
>
> Chad
>
> Paresh Khatri <Paresh.Khatri@aapt.com.au> wrote:
> Hi Daniel,
>
> Why don't you use an inbound route-map (on the session with the Backbone
router) with a prefix-list to match on all longer prefixes of the aggregate
and tag them with a 'no-advertise' community ?
>
> Paresh.
>
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Daniel Berlinski
> Sent: Tuesday, 15 November 2005 02:00 PM
> To: ccielab@groupstudy.com
> Subject: BGP question
>
>
> Hi
>
> Please consider the following scenario:
> Backbone --- R3 --- R1
>
> I'm summarizing incoming routes from Backbone in R3. I need to see in R1
only the summary route. I'm not permitted to use unsuppress-map or
summary-only keyword with aggregate-address in R3. My solution needs to be
flexible with future additional routes coming from backbone:
>
> I've tried different things (unsuppress maps and prefix-list which is not
very scalable) and now I'm feeling totally out of track. Would not like to
be given the straight answer but just a hint to put me in the right
direction would help in this one.
>
> Cheers
>
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