Enterprise Multihoming

Thu Mar 11 16:40:46 UTC 2004

Mutli-homing a non-ISP network or system on multiple carriers is a good 
way to maintain independent links to the internet by means of different 
peering, uplinks, over-all routing and reliability.  My network on NAIS 
is currently multi-homed through AT&T.  I use a single provider as both 
of my redundant links via 100% Fiber network.  Even though this is 
cheaper for me, all it takes is for AT&T to have some major outage and I 
will be screwed.  If I have a backup fiber line from say, Global 
Crossing, then it doesn't matter if AT&T takes a nose dive, I still have 
my redundancy there.

That is why most non-ISPs hold multihoming via different providers as 
their #1 choice.

Greg

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?
>
>Flame on. :-)
>
>Thanks,
>John
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