From: Peter van Oene (pvo@usermail.com)
Date: Tue Nov 12 2002 - 16:08:33 GMT-3
On Tue, 2002-11-12 at 17:06, Joe A wrote:
> Group,
>
> I don't 'conclusively' agree with the 'aggregation theory' for this
> reason: say I have network A.A.A.A /24 from ISP A and network B.B.B.B
> /24 from ISP B, and both are chunks out of a class A or B, anything that
> can be aggregated on the ISP's egress. If I also advertise A.A.A.A /24
> to ISP B and B.B.B.B /24 to ISP A, then, assuming they propagate the
> routes I send, their advertisement will be the more specific match, and
> I'd be pulling traffic in exactly opposite of what I expected!
This _may_ occur, but likely a few things would prevent it from
happening in the first place. Primarily, when you call ISP B and
explain that you are sending them A's space, they _should_ ask you to
provide a letter (MOU) from A giving A's permission for you to do this.
Otherwise, they should not accept that advertisement. If A gives you
the letter, than they should be smart enough to leak the same space
themselves to prevent the sub-optimal routing you describe.
Of additional note, even if you did manage to get this running, you
would still revieve traffic from A and all of A's single homed customers
directly down your A link, though you would tend to see some flow
through B as you describe.
I
> haven't seen this to be the case, so I have to disagree that they will
> not propagate a /24. I think if you have a discussion with your
> providers and you all understand your goals, they'll either accommodate
> you or tell you they can't; either way there should not be any
> surprises.
Discussion is the key.
>
> All that aside, these are the problems that the RADB was designed to
> solve, right? Get your routing policy documented in a public database
> so that all providers can easily see your policy and know that you are
> in fact sending out /24s. I'm curious, does anyone out there 'really'
> use the RADB when they do their BGP configs?
I am aware of providers who do build their configs from RADB and
associated mirrors. However, I would tend to think that in many cases,
manual intervention is required to tune policies due to inconsistencies
the database.
> Joe
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Larson, Chris
> Sent: Tuesday, November 12, 2002 10:46 AM
> To: 'Paul Jin'; MADMAN; Hamele Kassa
> Cc: Brian T. Albert; ccielab@groupstudy.com
> Subject: RE: BGP & multihoming
>
>
> Although most ISP's will accept the /24 it is unlikely that they
> propogate it outside of their own AS if the IP block you have was
> provided by the ISP. In that case they will accept /24 but will usually
> aggregate it to neighbors outside of their own AS.
>
> > -----Original Message-----
> > From: Paul Jin [SMTP:pauljin@yahoo.com]
> > Sent: Monday, November 11, 2002 8:05 PM
> > To: MADMAN; Hamele Kassa
> > Cc: Brian T. Albert; ccielab@groupstudy.com
> > Subject: Re: BGP & multihoming
> >
> > I cannot remember who it was for sure, but I had a situation where I
> > got for a customer of ours, to advertise a customer owned /24 to ATT
> > and they had no problems.
> >
> > Everything went fine, and a week or two later, I got a call from the
> > customer saying there is a particular web site that the executive
> > members needed to get to but somehow they could not since the change
> > over to ATT.
> >
> > What we found out was the fact that although ATT took in the /24
> > prefix and readvertised it, there was an ISP few hops down that did
> > not accept /24. and the web server that the customer needed to get to
>
> > was behind that ISP.
> >
> > But I cannot remember who it was, and this was back in early part of
> > 2001.
> >
> > Has anyone had any similar experience?
> >
> > - Paul
> >
> > MADMAN <dave@interprise.com> wrote:I keep seeing people refer to this
>
> > /19 as the smallest aggregate that will be accepted by a provider
> > though I have yet to meet this provider. I have set up several
> > customers with dual home full routes and they announce a single /24
> > network or maybe a couple but very few have /19 or better. The
> > providers I have worked with that accepted the /24 include Qwest, MCI,
>
> > Sprint, Onvoy, and AT&T come to mind.
> >
> > Dave
> >
> > Hamele Kassa wrote:
> > >
> > > Brian,
> > >
> > > You do not need to secure your own registered address/es(your
> > > network
> > has to
> > > be bigger than /19 space to qualify). The IP address/es assigned to
> > > you from your providers (/24 or shorter address space) will work for
>
> > > you as long as you are running BGP(no longer prefix than /24).
> > > However you need
> > to
> > > secure and AS from ARIN(if you are multihomed you will qualify).
> > >
> > > I hope this helps.
> > >
> > > HK
> > >
> > > ----- Original Message -----
> > > From: "Brian T. Albert"
> >
> > > To: "MADMAN"
> > > Cc:
> > > Sent: Sunday, November 10, 2002 10:51 AM
> > > Subject: RE: BGP & multihoming
> > >
> > > > When you say "your own registered address/es", do you mean
> > > > prefixes
> > > assigned
> > > > to you from your 2 providers or obtained from another authority?
> > > > What
> > > other
> > > > authority can assign you prefixes independent of you providers,
> > > > and
> > what
> > > are
> > > > the requirements to obtain them?
> > > >
> > > > BA
> > > >
> > > > -----Original Message-----
> > > > From: MADMAN [mailto:dave@interprise.com]
> > > > Sent: Saturday, November 09, 2002 9:12 PM
> > > > To: Brian T. Albert
> > > > Cc: ccielab@groupstudy.com
> > > > Subject: Re: BGP & multihoming
> > > >
> > > >
> > > >
> > > > You don't need NAT if you have your own registered address/es. No
> > > special
> > > > config required, you simply announce your public address/es
> > > >
> > > > Dave
> > > >
> > > > "Brian T. Albert" wrote:
> > > >
> > > > > In the real world can BGP multihoming to 2 different providers
> > > > > be accomplished without NAT for the internal networks? I have
> > > > > found
> > some
> > > > links
> > > > > on CCO http://www.cisco.com/warp/public/459/BGP-PIX.htm that
> > > > > show
> > how to
> > > > do
> > > > > it with NAT, but is it possible without. If so, can someone
> > > > > supply
> > some
> > > > > config examples or good links.
> > > > >
> > > > > Thanks
> > > > >
> > > > > Brian T. Albert
> > > > > brian.albert@worldnet.att.net
> > > >
> > > > --
> > > > David Madland
> > > > CCIE# 2016
> > > > Sr. Network Engineer
> > > > Qwest Communications Inc.
> > > > 612-664-3367
> > > > dave@interprise.com
> > > >
> >
> > --
> > David Madland
> > CCIE# 2016
> > Sr. Network Engineer
> > Qwest Communications
> > 612-664-3367
> >
> > "You don't make the poor richer by making the rich poorer." --Winston
> > Churchill
> >
> >
> > ---------------------------------
> > Do you Yahoo!?
> > U2 on LAUNCH - Exclusive medley & videos from Greatest Hits CD
This archive was generated by hypermail 2.1.4 : Tue Dec 03 2002 - 07:22:58 GMT-3