From: Peter van Oene (pvo@usermail.com)
Date: Tue Feb 18 2003 - 19:48:38 GMT-3
At 05:21 PM 2/18/2003 -0500, trust.hogo@sarcom.com wrote:
>The aggregate-address statement is correct. The route will be advertised as
>if you are the originator but it will also indicate that's its missing info.
>I hope the following will help clarify. From The Command Reference guide:
Ok, lets look at the below. My point was that you cannot "summarize" a /24
with a /24.
>Usage Guidelines
>
>You can implement aggregate routing in BGP and multiprotocol BGP either by
>redistributing an aggregate route into BGP or multiprotocol BGP, or by using
>this conditional aggregate routing feature.
>
>Using the aggregate-address command with no keywords will create an
>aggregate entry in the BGP or multiprotocol BGP routing table if any
>more-specific BGP
^^^^^^ /24 is equally specific as /24, not more.
> or multiprotocol BGP routes are available that fall in the
>specified range. The aggregate route will be advertised as coming from your
>autonomous system and will have the atomic aggregate attribute set to show
>that information might be missing. (By default, the atomic aggregate
>attribute is set unless you specify the as-set keyword.)
Of note, 1771 suggests that as-set be set by default. Cisco behaves
somewhat contrary to the spec by default. Juniper and others conform by
default which can create some neat issues.
>Using the as-set keyword creates an aggregate entry using the same rules
>that the command follows without this keyword, but the path advertised for
>this route will be an AS_SET consisting of all elements contained in all
>paths that are being summarized. Do not use this form of the
>aggregate-address command when aggregating many paths, because this route
>must be continually withdrawn and reupdated as autonomous system path
>reachability information for the summarized routes changes.
>
>Thanks
>
>Trusth
>
>-----Original Message-----
>From: Peter van Oene [mailto:pvo@usermail.com]
>Sent: Tuesday, February 18, 2003 12:54 PM
>To: ccielab@groupstudy.com
>Subject: RE: GBP Question
>
>
>At 09:22 AM 2/18/2003 -0500, Cameron, John wrote:
> >Use the following on Router B:
> >
> >aggregate-address 150.50.31.0 255.255.255.0 summary-only
>
>For what its worth, this is an entirely different route than the original
>path. Why not just filter the incoming route and announce your own if we
>are taking that much liberty? Of note, I'm not entirely sure that the
>aggregate-address command will accept a prefix of the same depth for a
>contributor. Indeed, if it did, this would seem broken to me.
>
> >This will remove Router A as the originator of the prefix
> >an make it "look" as if Router C ownes the prefix.
>
>This will create two routes in the network where one previously
>existed. In my books, this wouldn't be a valid answer to the question,
>then again I expect I wouldn't ask for BGP to be broken in the question.
>
>Pete
>
>
> >HTH,
> >JDC
> >
> >
> >-----Original Message-----
> >From: love cisco [mailto:love_cisco@hotmail.com]
> >Sent: Tuesday, February 18, 2003 5:07 AM
> >To: ccielab@groupstudy.com
> >Subject: GBP Question
> >
> >
> >I have a question about filtering BGP As number in AS path table.
> >
> >Router A has a ip address 150.50.31.1/24 distributed in bgp AS100. In
> >Router C bgp table, you will see the 150.50.31.0 network as-path is
> >"200 100". My question is how to config bgp in router B to filtering as
> >path number 100. So router C will only 150.50.31.0 network as-path is
> >"200"?
> >
> > ------------ ------------ ------------
> > | Router A |------------| Router B |--------------| Router C |
> > | AS 100 | | AS 200 | | AS 300 |
> > ------------ ------------ ------------
> > 150.50.31.1/24
> >
> >_________________________________________________________________
> >OmSCJ@=gIOWn4s5D5gWSSJ<~O5M3!* MSN Hotmail!# http://www.hotmail.com
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