Enterprise Multihoming

Daniel Roesen <dr@cluenet.de> 3/11/04 9:13:04 AM >>>

For the past few years it has been fairly common for non-ISPs to
multihome to different providers for additional redundancy in case


single provider has problems. I know this is frowned upon now,
especially since it helped increase the number of autonomous systems


routing table prefixes beyond what was really necessary.

Who defines what is "really necessary"? What is your understanding
of "really necessary" when it comes to the desire to be commercially
and technically independent of your suppliers?

It's this discussion again.

That goes off in entirely the wrong direction but I guess I'll clarify
that statement. :slight_smile: My point was that most companies could have met
their connectivity requirements by simply getting multiple connections
to the same provider from the beginning. However, among the
less-technical managers it seemed to be popular to demand connectivity
to multiple ISPs. It seems that me that this was not really necessary
from a technical perspective in many cases, it just made people feel

I don't really want to focus on that, though; I'm more interested in
the situation as it stands today. If a company were going to add brand
new Internet connectivity where it didn't exist before, what factors
would you use to determine if multiple ISPs should even be considered?

Given the stability of the larger ISPs and the general lack of true BGP
expertise at many companies, is the potential benefit of multihoming to
different ISPs worth the added risk and responsbility that comes with
using BGP?

Our BGP configuration isn't very difficult to understand but we do have
a lack of BGP knowledge in the department and some additional training
is in order. However, might it not be better to just simplify our
connectivity and remove BGP altogether? Sure, I like BGP as much as the
next guy but there's no sense in running it just because we can. :slight_smile:


In my opinion, these are all decisions that each company and it's management
and IT departments must reach for themselves. There are no universally right
or wrong answers. There are tradeoffs either way, and, evaluating those
tradeoffs is a big part of why an IT department and managers get paid.

For some companies, a single connection might be all they need.

For others, multiple circuits to a provider they think is reliable enough
may do the trick.

Many companies may feel they need more than that, so, they may choose to
go to BGP and true multihoming.

Any of those answers can be the right answer. There are other possible
"right" answers too. The important thing is for the IT department to do
their homework on ALL the tradeoffs associated with each possible scenario,
and, help their management reach a decision that is right for the company.

As you mentioned, there are other risks to BGP and multihoming, and, additional
responsibilities that come with it. As such, the staff to meet those
responsibilities should be factored in as an additional cost in that solution.