Ethernet has self-assigned IP address, can't connect

[sschech]

Hi, I've seen some similar threads here but nothing that's 100% the equivalent of what I'm getting, so hoping by starting a new thread it might yield a few clues.

My hardware - 15" MacBook dual-booting Snow Leopard and Windows 7 (via Bootcamp).

I've had no problems networking the MacBook under either OS until I arrived in NYC last night to visit my mother. Now I'm getting the "Ethernet has self-assigned IP address" error that others have reported under various circumstances.

In this case, my mother uses Optimum Online as her ISP. I have checked her networking configuration (she uses WinXP) and everything is automatic - DHCP, DNS, etc, no user ID or password required for internet access.

I took the ethernet cable from her PC, plugged it into my MacBook, and I get the error with both Snow Leopard and Win7.

I have tried deleting the airport preferences file from the library, I have tried setting TCP/IP preferences manually and then going back to DHCP again, I have the firewall turned off, allow all connections. I have turned off Airport since there is no WiFi. There is no router, wired or wireless.

Because there's no router, trying to fix this is especially frustrating - I connect the cable to her PC, google around a bit for some possible answers, connect to my MacBook, apply the answers, reboot the MacBook, still doesn't work, reconnect the ethernet cable to her PC, google some more, repeat and repeat and repeat!

None of this is working. If I have to spend the next 7 days on her PC it will drive me crazy! (Because it's old and slow, because my files are all on my MacBook, etc.)

I'm almost ready to go out and buy a pocket WiFi travel router (except there are no guarantees that would solve the issue, right?)

Any thoughts, tips, ideas, jokes or lines from obscure movies (except "frankly my dear I don't give a damn!") would be most appreciated!

[hayne]

1) Some ISPs record the MAC address (Ethernet hardware address) of the computer using the connection and don't allow others. You might need to phone the ISP.
Or possibly spoof (modify) your Ethernet's MAC address (Google will find directions for this)

2) Are you sure that PPPoE is not required? This is common for DSL (phone) connections, less common for cable connections.

[fracai]

If it is a case of binding the MAC address, the proper procedure would be to open the network settings on the desktop and "Release" the DHCP lease. This should break the binding with the desktop MAC address and allow another MAC to be bound.

Regardless, get a router in there. Even if there's only one machine on the network it will protect against a slew of attacks that a directly connected machine is vulnerable to.

[sschech]

The thing is, as you might have guessed, I've visited my mother before. In the past, I had a Dell laptop. And I did just what I tried to do last night, yank the ethernet cable out of her PC and put it in the laptop and I was good to go. So I don't think it's a case of anything bound to a MAC address.

Nothing in her configuration has changed since my last visit, at least not as far as I can see. Same PC, same ISP and DSL modem. The only thing that's changed from my last visit is that I have now upgraded to Mac.

I did examine the network connections dialogs on her PC to see if there was anything along the lines of PPPoE and don't see anything like that in her configuration.

Fracai, I like your suggestion, never thought about it before, but she's running WinXP with an old version of Norton (without any anti-virus) and this would probably be a good addition for her. Thanks!

[hayne]

Quote: Originally Posted by sschech The thing is, as you might have guessed, I've visited my mother before. In the past, I had a Dell laptop. And I did just what I tried to do last night, yank the ethernet cable out of her PC and put it in the laptop and I was good to go. So I don't think it's a case of anything bound to a MAC address.

I've heard of ISPs that store a few MAC addresses and allow any of the previously seen ones, up to a limit. So it's possible that the limit is 2 and you're hitting it.

Quote: I did examine the network connections dialogs on her PC to see if there was anything along the lines of PPPoE and don't see anything like that in her configuration.

You should phone the ISP and ask if PPPoE is required and if they store MAC addresses.

[DeltaMac]

Optimum Online is a cable provider. You can power-cycle the cable modem, (leaving it off for maybe 2 minutes to make sure), and change your connection to your Mac. After the modem comes back on, it should then connect with your Mac.
That's assuming that your ISP allows it, as others have said.

[sschech]

Quote: Originally Posted by DeltaMac Optimum Online is a cable provider. You can power-cycle the cable modem, (leaving it off for maybe 2 minutes to make sure), and change your connection to your Mac. After the modem comes back on, it should then connect with your Mac. That's assuming that your ISP allows it, as others have said.

DeltaMac, can you hear the sound of me smacking my head and saying, "D-oh"? I'm totally embarrassed that I never thought to try this (write it off to jetlag?) and it worked just fine. Thanks!

Will probably go with getting my mother some sort of cheap router because of the probably-better firewall protection, as fracai noted.

Thanks again to all for your help!