Address portability all depends on if you IP blocks are assigned by ARIN/RIPE/APNIC/ISP portable or if you are using the ISP's address space. It has been my experience that multi-homing to diverse ISP's with multiple circuits per ISP (i.e. Primary/Secondary with ISP-A and Primary/Secondary with ISP-B) is the best option if you can afford the cost and your bandwidth requires it. Like it was stated before, if you can afford the possible downtime associated with multi-homing to a single ISP then yes there are definitely cost savings to be had and reduced administrative overhead; but, if you cannot afford the possibility of downtime then separate ISP's is the only way to go. Chris Burton Network Engineer Walt Disney Internet Group: Network Services The information contained in this e-mail message is confidential, intended only for the use of the individual or entity named above. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any review, dissemination, distribution or copying of this communication is strictly prohibited. If you have received this e-mail in error, please contact Walt Disney Internet Group at 206-664-4000. -----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Scott McGrath Sent: Friday, March 12, 2004 5:50 PM To: nanog@merit.edu Subject: Re: Enterprise Multihoming As Marshall noted multi-homing gives you the ability to switch providers easily. This ability also gives you leverage with your network providers since vendor lock-in does not exist. This is a strong business case for multihoming and is one the financial types understand and appreciate. In a prior incarnation I worked for a distributor who had a online ordering system. Our telcom coordinator got a "great" deal on bundled internet service and telephony from a unnamed vendor. Due to the peering arrangements the carrier had major customers were unable to place orders in a timely fashion. I set up a new AS and set up multihoming with another carrier and made our customers happy again. Subsequently said carrier had an outage which took down our link to them for 7 weeks. Since this was an internal problem at our provider multiple links to this carrier would not have benefited us in the least. A multihoming strategy also allows you to select providers who provide connectivty to your business partners and customers which is another win for obvious reasons. Scott C. McGrath On Thu, 11 Mar 2004, Marshall Eubanks wrote:

There is another thing - if you are multi-homed, and want to switch providers, it is pretty seamless and painless - no renumbering, no loss of connection, etc., as you always have a redundant path.

On Thursday, March 11, 2004, at 12:34 PM, Pekka Savola wrote:

...

<On Thu, 11 Mar 2004, Gregory Taylor wrote:

...

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.

Well, I think this, in many cases, boils down to being able to pick the right provider.

I mean, some providers go belly-up from time to time. Others are designed/run better.

For a major provider, complete outage of all of its customers is

such

...

a big thing they'll want to avoid it always. If it happens, for a brief moment, once in five years (for example), for most companies that's an acceptable level of risk.

-- Pekka Savola "You each name yourselves king, yet the Netcore Oy kingdom bleeds." Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

Regards Marshall Eubanks

T.M. Eubanks e-mail : marshall.eubanks@telesuite.com http://www.telesuite.com