Why can't I connect to router via ethernet?

[Black Landlord]

I've been trying to solve this most of the day.
My new iMac will connect to my belkin router via airport but when I turn off airport and plug it in via ethernet (the way the old mac was connected) I can't get anything... can't even log into the router. All diagnostics say internet disconnected. Done about 7,000 power cycles of all equipment, tried different ethernet cables in different positions on the router; had help from Apple to determine my ethernet was working; and the new mac seems to know when the router is powered down (disconnected cable message) so I know it's not a dead ethernet port.
Would appreciate any help.

[Joey Cupcakes]

In your Network settings, is your ethernet port set to DHCP?

[Wild eep]

Yes.

[freeradical]

Does your router do MAC address filtering? Your airport card and ethernet port have different MAC addresses. You might have to log in to your router and add the MAC address for the ethernet port.

[deckeda]

BL, just to confirm, you powered on the Belkin, waited until fully up, then hit its IP it with the Mac?

Try a different web browser also. Sounds stupid I know but has been known to work.

[space-time]

[quote Wild eep]Yes.
why do you answer a question addressed to Black Landlord? how many multiple personalities are you? have you seen a psychiatrist?

[Black Landlord]

[quote space-time][quote Wild eep]Yes.
why do you answer a question addressed to Black Landlord? how many multiple personalities are you? have you seen a psychiatrist?
I appear to be the reason for wild eep's existence. I fantasize that he's a svelte 22 year old tousle-haired boy-next-door type, but he'd have had to have been about 12 when he came to forum land (possible, no?)

[Black Landlord]

[quote Joey Cupcakes]In your Network settings, is your ethernet port set to DHCP?
Yes, thanks. DSL modem connects to router via PPoE, and router to mac via DHCP as I understand it. I tried using the settings on the old mac as a reference as well.

[Black Landlord]

[quote freeradical]Does your router do MAC address filtering? Your airport card and ethernet port have different MAC addresses. You might have to log in to your router and add the MAC address for the ethernet port.
Yeah MAC address filtering is in place and AP card is enabled. This is an excellent tip-- didn't realize...

[Black Landlord]

[quote deckeda]BL, just to confirm, you powered on the Belkin, waited until fully up, then hit its IP it with the Mac?

Try a different web browser also. Sounds stupid I know but has been known to work.
Yes, and tried. Thanks-- I don't have a lot of experience with hard-wired networking and ethernet settings, so no suggestion is too basic.