Ethernet not working on RPI - my fault or the pi's?

Have you tested the cable/connection with a different computer?  Does that work?

I though I had a problem like this but I found that it was the connection/cable.  I wigglied it about and this got it working.  Maybe try a different cable.

I've tried 2 different cables that both worked from my laptop to the router. I tried directly connecting the laptop to the pi with the cables (i read somewhere the port can auto-sense and crossover appropriately) and neither worked...

Ewan Watson wrote:

 

I've tried 2 different cables that both worked from my laptop to the router. I tried directly connecting the laptop to the pi with the cables (i read somewhere the port can auto-sense and crossover appropriately) and neither worked...

Are you using a router that is DHCP active?

Yes I am. Though I have tried manually assigning static IPs for the router and (of course) for the direct to laptop connection. I didn't even get a link light though which is why I am concerned that the problem is lower level than IP

Can I just confirm something. 

The RPi is connected to a cable (that works) and the cable is then connected to a socket on your router (that you know works).

Correct?

Yes. The RPi has been connected using 2 cables (that both work) to each of the 4 ports on the router (that all work). At no time did the raspberry pi show any lights or successfully ping anything (using dhcp or static)

If "ip link ls eth0" displays a MAC address on the second line of output (link/ether) then it's a near certainty that everything is fine at interface link level, and all you need is a proper cable to your Ethernet switch or router for all the link LEDs to light up like a Christmas tree.  It's just a hardware problem so focus on getting those lights to appear before worrying about IP addresses or network configuration.  DHCP, IP addresses, and routing aren't relevant until your link lights are lit.

Your tests so far seem to have eliminated the leads and the other end of the Ethernet connection though, so it rather looks like there could be a physical problem on the board.  Have a very close look at the Pi in the vicinity of the RJ45 looking for anomalies like poor solder joints, and peer inside the connector for any bent pins.

It sounds you have network problems.  I can only see three possible issues:

1. Your router is not giving out IP addresses for so reason / does not like the RPi .

2. One of the files that you modified is not correct (a fresh image would fix this)

3. Your RPi is not functioning correctly (but I don't think this is the problem)

Try re-imaging your SD card and start-up with the cable ethernet plugged in.  The other casue could be your power supply. Check: http://elinux.org/RPi_VerifiedPeripherals#Power_adapters to see if you have a problem power supply.

Thanks for that. I'm pretty sure I saw a mac address somewhere in testing and figured that meant the port was getting power but I just wasn't able to make it happy. I was thinking about making a loopback ethernet adapter but thats about as close as I go to technical. I'll check out the board when i get home (in about an hour) and see if anything is out of whack (but wouldn't know where to begin with fixing it..)

The first batch of RPI's that were sent out had faulty Ethernet port and the Foundation has - will replace then if you get in touch with them