From: Nick Shah (nshah@connect.com.au)
Date: Wed Sep 25 2002 - 04:03:02 GMT-3
Khalid, yes you are right.
In a hurry, I misread the requirement.
Nick
----- Original Message -----
From: Khalid Siddiq <khalid@sys.net.pk>
To: Nick Shah <nshah@connect.com.au>; Young K. Bae <ybae@cisco.com>;
<ccielab@groupstudy.com>
Sent: Wednesday, September 25, 2002 4:22 PM
Subject: RE: Need a verification on a BGP solution
> Nick,
> the requirement is, R5 advertise only an aggregate address to R4, but not
to R2.
> i belive that we have to filter the aggregate route on R2 also.
> please calirfy if i am wrong
> regards
> khalid
> -----Original Message-----
> From: Nick Shah [mailto:nshah@connect.com.au]
> Sent: Wednesday, September 25, 2002 6:21 AM
> To: Young K. Bae; ccielab@groupstudy.com
> Subject: Re: Need a verification on a BGP solution
>
>
> Young,
>
> comments inline...
>
> > R5 has two EBGP peers - R2 and R4. R5 has five routes in its BGP
table -
> > 192.168.112.0, 192.168.113.0, 192.168.114.0, 192.168.115.0, and
> > 172.109.109.0. All of these are /24 routes. The first objective is for
> R5
> > to not advertise 172.109.109.0 to both R2 and R4. The second objective
is
> > for R5 to advertise only an aggregate address to R4, but not to R2,
while
> > not advertising 192.168.112.0/24 to R2.
> >
> > The exact instruction from the IPExpert Lab#31 reads:
> >
> > "R5 should not advertise 172.109.109.0 to R2 or R4. R5 should advertise
a
> > single route for the Class C networks to R4. R2 should not have
> > 192.168.112.0 in its BGP or routing tables. Do not use an access-list."
>
> First you must construct aggregate address (without the summary only
> option). Then construct a prefix list for denying 172.109.109.0 &
> 192.168.112.0 & permitting everything else. Construct another prefix list
> for denying 172.109 & also denying 192.168.all/24 & permitting everything
> else or permit the /16 only (either way this will only permit the /16)
>
> Apply each of these to the respective neighbors.
>
> You could acheive similar results with Route-maps, and distribute lists &
> prefix lists out (there are a couple more 'screwy' ways apart from these
as
> well)If you are using distribute lists use prefix lists with it , instead
of
> access lists so as not to violate the conditions of the requirement.
>
> Your solution is also correct.
>
> rgds
> Nick
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