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Community Member

Troubleshooting Late Collisions

I want to back-up my cisco-3661 with a cisco-3620. Once I try to do a test on my 3620 the ethernet card will not come up and we get this error %AMDP2_FE-5-LATECOLL.

Community Member

Re: Troubleshooting Late Collisions

Late collisions are usually caused by duplex mismatches. Check both sides of your ethernet and verify that they're both half or full.


Community Member

Re: Troubleshooting Late Collisions

This can be a bad drop cable also, check equipment and connections.

Community Member

Re: Troubleshooting Late Collisions

In addition to what has been suggested , you may want to specifically check the following:

. Incorrect configuration

. Faulty hub or shared media device

. Faulty Network Interface Card (NIC) or switch port

. Excessive network traffic beyond the limations of the shared media hub or switch port.

If your router, switch, or NIC port is operating a full-duplex, collisions and late collisions should never occur.



Community Member

Re: Troubleshooting Late Collisions

Again in addition to the measures already outlined a late collision as opposed to a general collision could be the result of a breach of the ethernet rules and the particular ethernet network segment being too large.

CCO has this on late collisions:


Late Collisions

To allow collision detection to work properly, the time period in which collisions are detected is restricted (512 bit-times). For Ethernet, this is 51.2us (microseconds), and for Fast Ethernet, 5.12us. For Ethernet stations, collisions can be detected up to 51.2 microseconds after the beginning of the transmission, or in other words: up to the 512th bit of the frame.

When a collision is detected by a station after it has sent the 512th bit of its frame, this is counted as a late collision.

Late collisions are reported by the following error messages:

%AMDP2_FE-5-LATECOLL: AMDP2/FE 0/0/[dec], Late collision

%DEC21140-5-LATECOLL: [chars] transmit error

%ILACC-5-LATECOLL: Unit [DEC], late collision error

%LANCE-5-LATECOLL: Unit [DEC], late collision error

%PQUICC-5-LATECOLL: Unit [DEC], late collision error

%PQUICC_ETHER-5-LATECOLL: Unit [DEC], late collision error


%QUICC_ETHER-5-LATECOLL: Unit [DEC], late collision error

The exact error message depends on the platform. You can check the number of excessive collisions in the output of a show interface ethernet [interface number] command.

router#show interface ethernet 0

Ethernet0 is up, line protocol is up

Hardware is Lance, address is 0010.7b36.1be8 (bia 0010.7b36.1be8)

Internet address is

MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:06, output hang never

Last clearing of "show interface" counters never

Input queue: 1/75/1/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: random early detection(RED)

5 minute input rate 1000 bits/sec, 2 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

2058015 packets input, 233768993 bytes, 1 no buffer

Received 1880947 broadcasts, 0 runts, 0 giants, 1 throttles

3 input errors, 0 CRC, 0 frame, 0 overrun, 3 ignored

0 input packets with dribble condition detected

298036 packets output, 32280269 bytes, 0 underruns

0 output errors, 10 collisions, 0 interface resets

0 babbles, 0 late collision, 143 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out

Note that the station reporting the late collision is merely indicating the problem; it is generally not the cause of the problem. Possible causes are usually incorrect cabling or a non-compliant number of hubs in the network. Bad network interface cards (NICs) can also cause late collisions.


Regards and best of luck!


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