From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sun Jul 25 2004 - 03:30:26 GMT-3
Summarize a route to "overlap" the NAT pool. Example: Summarize a /24
subnet of a class B network to a /17. Use addresses that are
encompassed by the /17 for the NAT pool.
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: Joseph D. Phillips [mailto:josephdphillips@fastmail.us]
Sent: Saturday, July 24, 2004 11:20 PM
To: Brian Dennis; Larry Metzger; group study
Subject: RE: Using ip route to null 0 to advertise local network to BGP
peer
I'm not sure I understand your second option. Would you just make up
this summary route, whether or not you had an interface addressed within
that range?
On Sun, 25 Jul 2004 02:11:04 -0400, "Brian Dennis"
<bdennis@internetworkexpert.com> said:
> Here are a few:
>
> 1) Loopback interface
> 2) Summarizing another route to overlap the NAT pool
> 3) Secondary IP addressing
>
> I personally like option 2. Makes you think outside the box. I'll
have
> to add this to one of the new labs for the IEWB-RS workbook I'm
working
> on (along with IPv6 of course ;-)
>
> Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> bdennis@internetworkexpert.com
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987
> Direct: 775-745-6404 (Outside the US and Canada)
>
>
> -----Original Message-----
> From: Joseph D. Phillips [mailto:josephdphillips@fastmail.us]
> Sent: Saturday, July 24, 2004 10:54 PM
> To: Brian Dennis; Larry Metzger; group study
> Subject: RE: Using ip route to null 0 to advertise local network to
BGP
> peer
>
> Such as? :)
>
> That's an interesting problem. So you're saying without the ip route
for
> a NAT pool to null 0, the route won't propagate to a BGP peer? Or is
> that what Solie & Lynch are saying?
>
>
> On Sun, 25 Jul 2004 01:22:49 -0400, "Brian Dennis"
> <bdennis@internetworkexpert.com> said:
> > If they are being nice they would let you use a static route but
there
> > are other methods to advertising a NAT pool.
> >
> > Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
> > bdennis@internetworkexpert.com
> > Internetwork Expert, Inc.
> > http://www.InternetworkExpert.com
> > Toll Free: 877-224-8987
> > Direct: 775-745-6404 (Outside the US and Canada)
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Larry Metzger
> > Sent: Saturday, July 24, 2004 10:03 PM
> > To: 'group study'
> > Subject: RE: Using ip route to null 0 to advertise local network to
> BGP
> > peer
> >
> > For clarification....
> > The example that you are referring to is using NAT and the route
to
> > null 0 is for the placement of a route to an address that otherwise
> does
> > not exist. I haven't taken my exam yet, but I will venture to guess
> > that this would be allowed if the situation was using NAT.
> >
> > What would you say in this case???
> >
> > Larry
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > James
> > Sent: Saturday, July 24, 2004 8:44 PM
> > To: Joseph D. Phillips
> > Cc: group study
> > Subject: Re: Using ip route to null 0 to advertise local network to
> BGP
> > peer
> >
> > On Sat, Jul 24, 2004 at 08:12:37PM -0700, Joseph D. Phillips wrote:
> > > I notice in a couple places, Karl Solie and Leah Lynch, in CCIE
> > > Practical Studies II, use a static route to null 0 in order to
make
> > sure
> > > that a local network advertises properly to a BGP peer.
> >
> > What Karl and Leah had done is mostly done in real-world
environment,
> > where it
> > is recommended that an AS always null-route w/ high A.D. their
> aggregate
> > to
> > prevent route-looping up to whomever they have default-route or less
> > specific
> > route pointed to (also to stabilize their BGP announcements when
their
> > internal
> > IGP or connected interfaces holding the announced routes begin
> > flapping). This
> > seems like to be a BCP amongst most people doing BGP.
> >
> > > For example, on page 805, there is an explicit advertisement of
the
> > > 191.19.42.0/24 net within BGP, and just to be on the "safe" side,
> they
> > > added: ip route 191.19.42.0 255.255.255.0 null0 253
> > >
> > > I understand the need for a high administrative distance on the
> static
> > > route, but is this kind of route allowed in the lab exam?
> >
> > Since it is statically/manually configured, IMHO it constitutes
static
> > route.
> > So I think it is safer to stay away from doing that in lab unless
you
> > are
> > permitted to do so.
> >
> > >
> > > Is it one of those real world things we're not allowed to do on
lab
> > day?
> >
> > Sounds like it. :)
> >
> > Since BGP scans rib before announcing a prefix, the only course of
> > action w/o
> > null route is probably to create loopbacks and assign addrs there..
> >
> > -J
> >
> >
> > --
> > James Jun TowardEX
> > Technologies, Inc.
> > Technical Lead Network Design, Consulting, IT
> > Outsourcing
> > james@towardex.com Boston-based Colocation &
> Bandwidth
> > Services
> > cell: 1(978)-394-2867 web: http://www.towardex.com , noc:
> > www.twdx.net
> >
> >
>
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