[isp-bgp] Re: Routing Information

[James <haesu@...>]

if you were to have your layer3 switch advertise the /24 upstream to your two
border routers, it is advisable to use an IBGP setup with an underlying OSPF.

have ibgp configuration on each equipment peer up to the loopback address.
you want to peer up with loopback address to ensure stable operation when one
of your interfaces go down. you need ospf to distribute the loopbacks, although
you can manually static route them which is more or less makeshift.

in other words, you have ibgp setup between all 3 equipments to distribute the
routes. but the peering address (aka. neighbor a.b.c.d statement) will be a
loopback address of each equipment, which can be carried in OSPF.

-J



On Sun, Feb 29, 2004 at 03:30:37PM -0500, Serge Paquin wrote:
> So is there a reason to use OSPF or another protocol?  I can't see what it
> gives me.  I figure iBGP would do everything I need.
> 
> Serge.
> 
> ----- Original Message ----- 
> From: "Pete Templin" <petelists@...>
> To: <isp-bgp@isp-bgp.com>
> Sent: Sunday, February 29, 2004 2:49 PM
> Subject: [isp-bgp] Re: Routing Information
> 
> 
> >
> > James wrote:
> > >>When using IBGP internally is it typical to use internal AS#'s for the
> > >>internal routers/switches or do you use them all with your AS# and the
> > >>next-hop parameter?
> > >
> > >
> > > when using IBGP:
> > > *) all routers in IBGP chain must speak using same ASN
> > > *) all routers in IBGP must be peered in full mesh[1]
> > > [1]: exception of rr's
> >
> > Or use confederations...
> >
> > >>I'm thinking that it may be wise for me to have my Layer3 Switch
> advertise
> > >>my address blocks to my routers.  That way the routers will advertise to
> > >>each other also.
> > >
> > > my line of thinking is this. if you have both routers right now as
> > > you currently have, joined in IBGP peering, each announcing a /24..
> > > it doesn't seem to make a lot of difference to me than your current
> > > setup. what happens if one of the router's Ethernet to switch goes
> > > down? yes, it will realize its gone, so it will withdraw the
> announcement
> > > which will then still propagate to your upstream and cause a flap
> anyway.
> > > if you use floating static route to null on each router, even if the
> ethernet
> > > goes down, it will continue advertising the prefix as its manually
> announced
> > > using network a.b.c.d command.
> >
> > Two routers peered by IBGP will SHARE their internal routes.  If ONE
> > router loses connectivity to the switch, the other router will continue
> > to announce the route to all IBGP routers, which will propagate the
> > route to appropriate EBGP peers based on the local policy.  The route
> > will not flap (assuming all parameters stay the same) to the outside
> world.
> >
> >
> >




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> 




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-- 
James Jun                                            TowardEX Technologies, Inc.
Technical Lead                        Network Design, Consulting, IT Outsourcing
james@...                  Boston-based Colocation & Bandwidth Services
cell: 1(978)-394-2867           web: http://www.towardex.com , noc: www.twdx.net






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        - ISPCON Spring 2004 - Washington DC Hilton & Towers -

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              - Informative. Substantive. Instructive -
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