From: Jonathan V Hays (jhays@jtan.com)
Date: Fri Sep 12 2003 - 17:03:51 GMT-3
Paul,
Respectfully, I must disagree. (I hope I'm still a list member after
this post. ;-)
Reconfiguring an AS with confederations *will* solve the BGP
synchronization problem. Note that we are discussing CCIE lab scenarios
here, not what might be reasonable in 'Real Life.'
To review, when BGP Synchronization is turned ON, a router cannot
advertise a BGP route to its iBGP neighbor (Internal BGP) unless the
route is known by an IGP such as OSPF, RIP, ISIS, etc. This
synchronization rule does *not* apply to eBGP (External BGP), which
means that a router will indeed advertise a BGP route to its eBGP
neighbor even if it is not known by an IGP. Reachability problems might
ensue due to lack of an IGP route - but that's another issue.
For example,suppose you have AS 100 consisting of R10, R20, and R30 with
BGP sync turned ON and no supporting IGP. You can configure each router
with its own confederation (each of which belongs to AS 100) to force
the routers to advertise BGP routes to each other. The trick is that
confederations run eBGP between each sub-AS, so if R10, R20, and R30 now
below to sub-ASs (confederation autonomous systems) 65010, 65020, 65030
they WILL advertise prefixes to each other, regardless of the existence
of those prefixes in the IGP, just like 'real' eBGP connections.
HTH,
Jonathan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Paul Borghese
Sent: Friday, September 12, 2003 1:27 PM
To: 'yu chunyan'; Kaiser_anwar@hotmail.com; ccielab@groupstudy.com
Subject: RE: alternative bgp no sync command
I can not see how confederations would help eliminate a BGP SYNC problem
..
if anything it will exasperate the problem.
Take care,
Paul
-----Original Message-----
From: yu chunyan [mailto:yuchunyan@hotmail.com]
Sent: Friday, September 12, 2003 10:58 AM
To: pborghese@groupstudy.com; Kaiser_anwar@hotmail.com;
ccielab@groupstudy.com
Subject: RE: alternative bgp no sync command
confederation works here ?
Bin
>From: "Paul Borghese" <pborghese@groupstudy.com>
>Reply-To: "Paul Borghese" <pborghese@groupstudy.com>
>To: "'Kaiser Anwar'" <Kaiser_anwar@hotmail.com>,
<ccielab@groupstudy.com>
>Subject: RE: alternative bgp no sync command
>Date: Fri, 12 Sep 2003 10:50:09 -0400
>
>Redistribute your BGP routes into your IGP protocol. With
synchronization
>enabled, BGP will not advertise routes to an EBGP speaker unless that
route
>is also known via the IGP protocol.
>
>Take care,
>
>Paul Borghese
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Kaiser Anwar
>Sent: Friday, September 12, 2003 10:18 AM
>To: ccielab@groupstudy.com
>Subject: alternative bgp no sync command
>
>Hi Group,
> I have a question about no sync command for bgp.I was
doing a
>lab
>with three routers running IBGP. I did not have the No sync command.
> what would be the alternative to No sync for bgp. Thanks
>
>
>Kaiser A
>
>
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