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RE: Confussion over multi-homing

  • From: Roeland M.J. Meyer
  • Date: Thu Sep 14 15:19:03 2000

David Lott: Thursday, September 14, 2000 10:34 AM wrote:

> First, allow me to state the assumptions that I'm under.  I understand
> the policy to state that if a business needs to multi-home 
> and requires
> less space than a /20, then they should request this space from their
> ISP.  I also understand that there are filters at the /20 
> boundaries in
> order to minimize the size of the routing table.
> 
> Question:  Doesn't this break multi-homing for end users that 
> need less
> than a /20?

Yep, this has been a topic here before...no real resolution. You didn't
really need to prove the case, it has already been proven.

The only way that you can do it is to justify a /20 or larger, get
portable IP space from ARIN, and make your own peering arrangements with
your upstreams. Considering that you will probably burn the best part of
the /20 with distributed services, this increases your internal
administration costs substantially. What you will have is a very
low-density use net-block, but at least you can now multi-home and even
have some geographical independence, for multiple-site use. If you have
good admins, the whole thing can be folded/collapsed into about 20
physical servers, or less (Lintel boxen keep the costs low too, see:
VA-Linux, about two racks).

Is this wasteful of IP space? ...absolut!
Is this necessary? ...sometimes.

If you are building a H-Rel/Hi-Avail/Hi-Secure site(s), you ain't
getting there without multi-homing with at least three providers. If you
have multiple sites, you can't get there without multi-homing on an ASN
that will be advertised (at least a /20, probably a /19).

Do I tell clients this? ... absolut!
Have I done this for clients? ... Yep, and I ain't saying who for
either.



---
R O E L A N D  M .  J .  M E Y E R
CEO, Morgan Hill Software Company, Inc.
Managing Architect
Tel: (925)373-3954
Fax: (925)373-9781
http://staff.mhsc.com/rmeyer