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No link to an Ethernet device

Core Issue

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 0
Ethernet0 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 1/255
Encapsulation ARPA, loopback not set, keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input never, output 10w5d, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 input packets with dribble condition detected
58853 packets output, 3531180 bytes, 0 underruns
58853 output errors, 0 collisions, 0 interface resets
0 babbles, 0 late collision, 0 deferred
58853 lost carrier, 0 no carrier
0 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:

  • If you have a hardware support contract directly with Cisco for this part, use the Service Order Submit Tool to request a replacement part directly.
  • For warranty service, contact the Cisco Technical Assistance Center (TAC) directly at 1-800-553-2447, or online by using the TAC Service Request Tool.
  • If your product is not covered by contract or warranty, contact your Cisco partner or reseller to request a replacement part for the hardware component that is causing the issue.