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Collision Problem

jim.normand
Level 1
Level 1

I have a Catalyst 6009 connected to a 3640. Port 2/1 on the 6009 is configured at 10MB/half as is port E0/0 on the 3640. I'm getting a lot of collisions on both ports. I have swapped the cable, changed the port on the 6009 to port 2/5 and changed the port on the 3640 to port E1/0. Cleared the counters for the ports and still I'm seeing many collisions.

Any thoughts would be greatly appreciated.

10 Replies 10

svermill
Level 4
Level 4

What is a "high" number? You should calculate this as a percentage of total packets and realize that there will always be some number of collisions. I think the official Cisco position is no more than .1% of packets result in collisions.

Hi,

The issue here is of speed and duplex setting.

Try setting the Duplex setting in router E0/0 interface and catalyst port as 10Mbps full forcibly.

If your router IOS doesn't give this option under interface mode or global mode, try upgrading the IOS ( I know thats pretty unusual!!) to 12.1 train.

The solution has been tested.

Hope that helps.

Daipayan

8042527 packets input

736926 collisions

which works out to be 9.16%

I have tried setting both ports to 10/half and 10/full but get the same results. I guess I should open a TAC case to see what Cisco has to say.

Thanks for your help!

tiz_1
Level 1
Level 1

Try setting the duplex of both interfaces to full duplex. I believe collisions are normal on half duplex links.

--Kevin

jliscano
Level 1
Level 1

I agree, full duplex the connection on the 3640 and the 6009. This also solved my issues as well.

To my understanding, the IOS supports 100MB/full duplex if I have those cards installed but I don't, I only have the 10MB cards installed that only support half-dulpex.

I have never seen a Cisco card that doesn't support full duplex unless you have an old hub . All Cisco's copper cards have the option of setting them to full duplex even they are single speed cards on the 6X00 series , change to full duplex will get rid of collisions ,collisions are a normal function on a half duplex link . The more traffic you have the more collisions you will have .

Thanks for your help. FYI...

According to Cisco, I need to get the (T) or "T-train" version of code on my router so it will support the full duplex function.

Jim

Jim,

Tell me more about that, did they also tell you which minimum version you should get? I would love to get the 3640's I have to run in FD mode.

Thanks, Maarten Sjouw.

I'm runnng the Enterprise/FW/IDS Plus IPSec 56 Feature Set. Based on the amount of memory that I have (16MB flash & 64MB dram), the latest image that I can run is 12.1(5)T9.

Hope this helps.

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