Late Collisions

Late Collisions

Another problem related to cabling is that of late collisions. These result in errors like the following:

unix: <ethernet_device>: no carrier: check Ethernet cable

The controller tried to transmit a packet but received a late collision signal from another machine. This usually indicates a problem in the Ethernet cable layout. The most frequent causes of this problem are excessively long cables and loose cable connections.

To isolate the problem, first look for violations of the Ethernet cable limits. For 10BASE5 cable (thicknet) the maximum segment length is 500m; for 10BASE2 cable (thinnet) the maximum segment length is 200m. The length of a transceiver cable (the cable that goes between a machine's Ethernet port and its transceiver) should not exceed 50meters. If all cables are within the specified limits and all connectors are firmly seated, this error could indicate a hardware problem in an Ethernet controller or transceiver. Some recommendations are:

Check other machines on the network for bad Ethernet controllers.
Check other machines on the network for bad transceivers. I f you suspect a bad transceiver, you can try swapping in a different one that works on another system.
Check to see if removing a certain machine from the network makes the problem change or disappear.