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Undersized packets

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6 replies

by jamie schnabel

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I just replaced all of my old switches with new Cisco Catalyst 3550 Switches. Everything is working great except for my IBM AS/400. The port that its plugged into is getting collisons and undersized packets. I have switched port, swapped the patch cable and hard set the port to the setting of the mainframes network cards. Does anyone have any suggestions or things to try. I am getting some strange things where the line does not go done between the switch and the as/400 but some of the clients sessions will stop communicating with the mainframe.

6 replies

by joseph moore

Did you try to turn on debugging on the switch, and pass some packets from the AS400 through the switch? Then look at the debug results and see how the packets look.

by pgm554

Set the card to 10 meg/ half duplex .If the problems go away,then you have a negotiation problem between the switch and card.

by cjnmis

If you have a Fluke LAN meter, I would suggest using that to help you determine the root cause of your problem.

If not, try dividing the number of collisions by the number of sent packets for that particular interface. If that number (in percentage) is greater than 1 or 2 percent then something else is the culprit.

Bear in mind that when using full duplex, you should "never" get collisions. If you have already tried hardcoding speed and duplex at both the switch and the AS/400, then youmay need to look at upgrading the NIC driver on the AS/400.

If you do switch to 10/half, you can expect to see collisions......

Hope this helps.

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