From: tan (tan@dia.janis.or.jp)
Date: Tue Feb 18 2003 - 23:07:17 GMT-3
Might the advertise-map option in aggregate command allow a /24 to be a
conditional candidate for the creation of a /24 aggregate? My logic is that
aggregate on its own looks for and collects only more-specific routes, but
the advertise-map option suppresses this autonomy and hands the routes to
the aggregate generation process. Might work...
This reminds me of a question I raised to myself last week reading a CCO
document, but thought it too mundane to track down.
Redisitribution, Network, and Aggregate all locally originate a route. But
downstream routers will prefer Redistributed and Network routes over
Aggregate routes according the to BGP best path selection algorithm.pdf on
CCO. This means the algorithm looks at something else but what this is not
elluded to in the obvious books and CCO links.
I am guessing it looks to see if the atomic attribute is set, but possibly
something else? I know it is mundane point, but anyone know?
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> trust.hogo@sarcom.com
> Sent: Wednesday, February 19, 2003 7:21 AM
> To: pvo@usermail.com; ccielab@groupstudy.com
> Subject: RE: GBP Question
>
>
> 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:
>
> 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 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.)
>
> 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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