From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Mon Oct 30 2006 - 18:07:19 ART
That is correct. You could also get around this problem with
the "allow-as-in" feature configured on the real AS 100. This will
allow them to accept BGP updates that have their own AS in the path.
HTH,
Brian McGahan, CCIE #8593 (R&S/SP)
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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> -----Original Message-----
> From: Mohamed Saeed [mailto:mohamed_saeed2@rayacorp.com]
> Sent: Monday, October 30, 2006 3:01 PM
> To: Brian McGahan; ccielab@groupstudy.com
> Subject: RE: IEWB - Ver3 - Lab 2 - Task 5.3 (Local-as)
>
> Hi Brian,
>
> Yes, the real AS 100 exists somewhere.
>
> I have revised the situation based on your clue.
>
> If SW1 does not use the "no-prepend" option, then it will advertise
the
> routes it receives from BB3 to other neighbors with the AS number 100
> existing in the AS path. When such a route arrives at the real AS 100,
> it will not be accepted. This will prevent the real AS 100 from having
> alternative route to the BGP subnets learned originated in AS 54.
>
> Am I right here or I am still missing something?
>
> Kind Regards
> Mohamed Saeed, CCNP - CCIP
>
> -----Original Message-----
> From: Brian McGahan [mailto:bmcgahan@internetworkexpert.com]
> Sent: Monday, October 30, 2006 10:43 PM
> To: Mohamed Saeed; ccielab@groupstudy.com
> Subject: RE: IEWB - Ver3 - Lab 2 - Task 5.3 (Local-as)
>
> Is the real AS 100 somewhere else in the topology? If so what happens
> when it receives the routes passed through BB3 if the no-prepend
option
> was not configured?
>
> Brian McGahan, CCIE #8593 (R&S/SP)
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Mohamed Saeed
> > Sent: Monday, October 30, 2006 1:34 PM
> > To: ccielab@groupstudy.com
> > Subject: IEWB - Ver3 - Lab 2 - Task 5.3 (Local-as)
> >
> > Hi All,
> >
> >
> >
> > In this task, it was required to configure SW1 to appear to BB3 as
if
> it
> > was in AS 100. The solution guide solved it as follow:
> >
> >
> >
> > On SW1:
> >
> >
> >
> > router bgp 400
> >
> > neighbor 204.12.1.254 local-as 100 no-prepend
> >
> >
> >
> > This way, BB3 will see the routes received from SW1 with AS path 100
> > 400.
> >
> >
> >
> > The "no-prepend" option was used here to prevent SW1 from prepending
> > this imaginary AS number (100) to the routes received from BB3. I do
> > agree that this should be done.
> >
> >
> >
> > My question is that using the "no-prepend" option was not explicitly
> > required in the task, will we lose points in a real lab exam for
using
> > it. What if we used the "replace-as" option also. It could be used
to
> > make BB3 sees the routes received from SW1 with AS path of 100.
> >
> >
> >
> > Regards
> >
> > Mohamed Saeed, CCNP - CCIP
> >
> >
>
This archive was generated by hypermail 2.1.4 : Wed Nov 01 2006 - 07:29:07 ART