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Re: Enterprise Multihoming

  • From: Jay Ford
  • Date: Thu Mar 11 11:20:57 2004

On Thu, 11 Mar 2004, John Neiberger wrote:
> On another list we've been having multihoming discussions again and I
> wanted to get some fresh opinions from you.
> For the past few years it has been fairly common for non-ISPs to
> multihome to different providers for additional redundancy in case a
> single provider has problems. I know this is frowned upon now,
> especially since it helped increase the number of autonomous systems and
> routing table prefixes beyond what was really necessary. It seems to me
> that a large number of companies that did this could just have well
> ordered multiple, geographically separate links to the same provider.
> What is the prevailing wisdom now? At what point do you feel that it is
> justified for a non-ISP to multihome to multiple providers? I ask
> because we have three links: two from Sprint and one from Global
> Crossing. I'm considering dropping the GC circuit and adding another
> geographically-diverse connection to Sprint, and then removing BGP from
> our routers.
> I see a few upsides to this, but are there any real downsides?

Many/most of my external connectivity problems are provider-related rather
than circuit-related.  Having two circuits to a single provider doesn't help
when that provider is broken.  I'm not saying that multi-ISP BGP-based
multi-homing is risk-free, but I don't see multi-circuit single-provider as a
viable alternative.

Jay Ford, Network Engineering Group, Information Technology Services
University of Iowa, Iowa City, IA 52242
email:, phone: 319-335-5555, fax: 319-335-2951

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