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Collision Problem @ 3640 router interface

In my 3640 router ethernet 0/0 port , collision is incresing like anything. Please suggest any one , how to slove the problem.

Note: i have 11 VLAN's in my Campus switch. Campus switch is 6009.

Router Report is below:

15293869 packets input, 1578129535 bytes, 0 no buffer

Received 5499754 broadcasts, 0 runts, 0 giants, 0 throttles

74 input errors, 0 CRC, 0 frame, 0 overrun, 74 ignored

0 input packets with dribble condition detected

2680061 packets output, 1615016285 bytes, 0 underruns

0 output errors, 165133 collisions, 0 interface resets

0 babbles, 0 late collision, 58456 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output buffers swapped out


Re: Collision Problem @ 3640 router interface

Hi -

Do a 'clear counters' on the 3640 and see how quickly your collisions rise and also please check ALL port speeds on the switch, make sure the speed on the switch port that is connected to the router is running on the same speed on both sides.

Thanks -

Re: Collision Problem @ 3640 router interface

Check that you are running the same duplex on both sides of the link. If the 6009 port is set to autonegotiate, then so must the 3640. If the 6009 port is forced 100-full, then so must the 3640.

What you must NOT have is the 6009 port forced 100-full, and the 3640 autonegotiating. If you do that, the 6009 will operate at 100-full, but it will not tell the 3640. So the 3640 will fall back to 100-half, and you'll get lots of collisions.


Re: Collision Problem @ 3640 router interface

165k collisions for 2 mill output is kind of high but not excessive. The 15 million packets input are what you are running into. Collisions are normal on half duplex. Its the CD part of CSMD/CD. As said earlier, clear counters and see what the current ratio is. You dont say what the interface is. Full duplex would get rid of collisions.

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Re: Collision Problem @ 3640 router interface

As there are no late collisions I would suggest the problem is more likely to be a duplex mismatch on either end of the link. ie. e0/0 full --> switch port half.

If a port, or interface detects another device trying to send at the same time as itself it will re-transmit in a randomly selected timeslot. If the re-transmit collides you will see late collisions. The absence of these indicates the re-transmitt information is being successfully sent.

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