There is no connectivity between the router and the Ethernet device. The interface may show down/down or up/down, as shown in this example of the show interface command output:
Router#show interface ethernet 0Ethernet0 is up, line protocol is down Hardware is QUICC Ethernet, address is 0002.b91d.9754 (bia 0002.b91d.9754)MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 252/255, load 1/255Encapsulation ARPA, loopback not set, keepalive set (10 sec)ARP type: ARPA, ARP Timeout 04:00:00Last input never, output 10w5d, output hang neverLast clearing of "show interface" counters neverQueueing strategy: fifoOutput queue 0/40, 0 drops; input queue 0/75, 0 drops5 minute input rate 0 bits/sec, 0 packets/sec5 minute output rate 0 bits/sec, 0 packets/sec0 packets input, 0 bytes, 0 no bufferReceived 0 broadcasts, 0 runts, 0 giants, 0 throttles0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort0 input packets with dribble condition detected58853 packets output, 3531180 bytes, 0 underruns58853 output errors, 0 collisions, 0 interface resets0 babbles, 0 late collision, 0 deferred58853 lost carrier, 0 no carrier0 output buffer failures, 0 output buffers swapped out
To insure you have the right type of cable refer,
Ethernet 100BaseTX and 10BaseT Cables: Guidelines and Specifications
On Cisco 800 series routers, check the router HUB/NO HUB button or TO HUB/TO PC button or the hub equivalent of the HUB/NO HUB button. For more information, refer Connecting Ethernet Devices section of Cisco 800 Series Routers Hardware Installation Guide
For more information, refer to Troubleshooting Ethernet.
When hardware replacement is indicated after troubleshooting: