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

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)

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.

Some things to try:

1. type in: ip link set up dev eth0 if this gets some of the remaining three lights to come on, then it's possibly a software issue.

2. ip link ls eth0 gives output similar to the following examples:

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000

    link/ether e1:14:51:ff:17:22 brd ff:ff:ff:ff:ff:ff

The important parts are the UP which tells you that the interface has been enabled and LOWER_UP which tells you that there's an active link to the device at the other end of the cable - you should have lights in this case.

2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT qlen 1000

    link/ether e1:14:51:ff:17:22 brd ff:ff:ff:ff:ff:ff

Here, the interface is enabled (UP), but NO-CARRIER tells us the link cannot be established to the other end.

2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN mode DEFAULT qlen 1000

    link/ether e1:14:51:ff:17:22 brd ff:ff:ff:ff:ff:ff

In this last example, where there's no UP, then the interface is DOWN and will not be attempting to bring the low level link up. Try ip link set up dev eth0 and see what happens.

One possible, but unlikely, reason for a NO-CARRIER indication could be that the device at the other end of the cable is configured to only connect at 1gigabit. The Pi can only manage 10/100 so this would cause it not to work. Alternatively, if 'autonegotiation' has been disabled on the switch/router then the connection will not be made unless you force the settings on the Pi to match.

Another good command to debug this is ethtool eth0 you'll get something like this:

Settings for eth0:

        Supported ports: [ TP MII ]

        Supported link modes:   10baseT/Half 10baseT/Full

                                100baseT/Half 100baseT/Full

        Supported pause frame use: No

        Supports auto-negotiation: Yes

        Advertised link modes:  10baseT/Half 10baseT/Full

                                100baseT/Half 100baseT/Full

        Advertised pause frame use: Symmetric Receive-only

        Advertised auto-negotiation: Yes

        Link partner advertised link modes:  10baseT/Half 10baseT/Full

                                             100baseT/Half 100baseT/Full

        Link partner advertised pause frame use: Symmetric

        Link partner advertised auto-negotiation: Yes

        Speed: 100Mb/s

        Duplex: Full

        Port: MII

        PHYAD: 1

        Transceiver: internal

        Auto-negotiation: on

        Current message level: 0x00000007 (7)

                               drv probe link

        Link detected: yes

Interesting stuff highlighted.  If there's no matching modes between Advertised link modes & Link partner advertised link modes then you'll have a problem.

Thanks everyone for your help and particularly selsinork for your comprehensive list of tests.

From memory I had eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> but I'll need to go back and check.

I tried plugging the pi into another two computers with a third ethernet cable last night and used a 5v1a phone charger to try charging the pi with no luck.

I glanced briefly at the connectors and saw nothing obvious but I wouldn't really know what I was looking for...