I've got my setup as Cable Modem > Router Hub > Airport Extreme. Have you tried it that way.

Did any of you other Earthlink customers receive the following email from Earthlink?

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"Dear EarthLink DSL Subscriber,

We are making changes to our network, beginning
June 24, 2003, after which you will no longer be able
to connect multiple computers to the Internet with a
single DSL connection, as you may have done in the past.

We apologize for any inconvenience this network
change may cause you.

The Terms and Conditions of your EarthLink DSL
service only allow for one computer to use your
EarthLink DSL connection at a time.

If you would like to use your DSL connection on multiple
computers at the same time, please check out
EarthLink Home Networking, which will allow all the
computers in your home access to the Internet at the
same time for one low price of $9.95 per month on top
of your regular DSL monthly fees:

http://www.earthlink.net/home/broadband/homenetwork/

If you have any questions about this policy, or about home
networking in general, please don't hesitate to let us
know. You'll find help in a hurry at the EarthLink Support
Center:

http://support.earthlink.net

Click on "Contact Us By Live Chat" to trade helpful, real-
time messages with a friendly Live Chat representative.
Or to send us an email, click on "Contact Us By Email."

Your business is important to us, and we work hard to
give you the best possible service.

Thank you for choosing EarthLink.

Sincerely,

The EarthLink High Speed Internet Service Team

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I called the tech support number and started asking questions. The guy I spoke with was nice but seemed to be unaware of the above policy change. In informed him that I wouldn't mind pay them an extra $9.95 a month for a home networking solution, but not at the expense of having to drop back to OS 9.2.2 to do it. Apparently the gateway equipment they are using for their home networking still does not support OS X. I have a feeling that this will affect many Mac Earthlink users.

I posted this same email on the Apple support discussion site. A guy responded as follows:

I cannot believe that you will have a problem if you use a router of your own. You should not need any software from EarthLink to make an OS X box work behind a router and DSL modem.

I asked...

What do you think they may be saying? Are they speaking to someone who has a DSL modem with an ethernet hub on the other side that is tied to two PCs rather than a router? Your thoughts...

He responded...

Are they speaking to someone who has a DSL modem with an ethernet hub on the other side that is tied to two PCs rather than a router?

I guess if the first thing after DSL modem is a router, there won't be a problem.
The first thing that I have after the DSL modem is an AirPort Base Station. We'll see what happens in the June 24th.

Unfortunately, one of the things missing in the Airport base Station is MAC cloning (the ability to tell the router to set its apparent MAC address to another value - e.g., the same as one of your Macintoshes). Since I like to swap between using the Airport and docking directly (for the higher throughput and to get rid of the firewall/NAT easily), if my Earthlink connection was using MAC authentication I'd probably dust off my LinkSys BEFW11S4 router (which supports MAC cloning.)

(Aside: Apple uses the term "Ethernet Address" for what the Ethernet industry calls the "MAC address" (Media Access Layer), possibily in the hope of avoiding confusion with the truncated name of their computer brand. The Apple System Profiler will tell you the 12-hex-digit Ethernet address(es) of your Macintosh. The Airport Admin Utility will tell you the Ethernet address it presents to the DSL modem as "Ethernet (WAN):")

KrecJ -
It's expected your Airport and iMac will have different Ethernet/MAC addresses. The datacom industry has gone to some effort to ensure that all Ethernet addresses everywhere are unique. (The exceptions are a few specialty devices specifically made to "clone" or "spoof" an address - generally for such things as routers (e.g. my LinkSys), test equipment and spy agencies.

It's not terribly common in DSL, more so in Cable broadband because of the nature of the wiring, for the Ethernet/MAC address to be locked to the account. "MAC Authentication"

As to me not getting the same eMail - well, first all DSL is local. There really is no Earthlink DSL monolith, just a patchwork of local DSL hubs and spokes from various providers. My services runs through Qwest and Covad (in fact, if I look up my assigned IP address at ARIN, it always shows as belonging to Covad. (For still more variety, the Earthlink backbone I'm fed into is actually part of the old MindSpring network Earthlink acquired five years ago - a topological anomaly that at least once a year causes someone at Earthlink to turn something off that's still needed to keep me connected - but that's just my problem!)

(If you visit DSL Reports and feed in your ZIP code you might find out more about your specific network. Presumably BellSouth is involved, at least with the wires.)

Finally, it's very hard to guess exactly what Earthlink's eMail to you is saying. It's possible they have previously allowed you to allocate more than one IP address from their hub and are now taking that away; in that case, they are perhaps just telling you that you need a Router where before you didn't (but of course they wouldn't point you at any specific router solution except the one they sell.) Or, they might be switching to MAC authentication (in which case you can just have them use the Ethernet/MAC address of your Airport (WAN) port.

It is theoretically possible that ISPs could detect the use of Routers and NATs running more than one computer and block it to force customers to purchase solutions from them, but to the best of my knowledge none in the US has done so. (I'm sure every time they look at LinkSys's sales figures they drool and think about it, though.)