transmission errors on Catalyst 2950 3

[malaize2]

Hi,

Our company uses a 24 port Cisco Catalyst 2950 switch. I was viewing the port stats and noticed that there are a lot of transmission errors and collisions on the 3 ports that are connected to 4 port hubs. Is this common when connected to a hub?

For example on port 16 there are 1,236,467 transmit errors (packets) and 205,446 undersized packets. The other 2 ports that are attached to hubs have similar stats.

Thanks, eli

 

[KiscoKid]

Are they 10mb hubs? Take a look at what speed and duplex the switch ports that connect to these hubs are set too.

You should either set the switch ports to auto speed and duplex or, if you know the hub type, hard set the switch ports to the same. i.e. if the hub is a 10mb half hub, set the switch port to 10mb half as well.

 

[jneiberger]

Collisions, and errors as a result of collisions, are normal and expected when using half duplex Ethernet.

FYI, it doesn't help us to know how many errors you have on the interface. The important thing is the ratio of errors to good frames. That number of errors would be high if you'd only transmitted five million frames, for example, but would not be significant if you had transmitted five billion frames in that same time period.

 

[jdeisenm]

I concur with previous posts.
Also, by definition a hub is half duplex.
Plug one device directly in to the switch port and do an ftp upload. Then re-insert the hub and plug the device into the hub and do the same ftp upload. Compare the results. You might get slightly better performance if you can replace the "hub" with a switch. Switches, by definition, can run at full duplex.

 

[malaize2]

Thank you all for the replies.

Two of the hubs run at 10/100 and the other runs at 100. The switch Duplex setting for the 3 ports was set to Auto. The switch Speed setting was also set to Auto. I changed the Duplex setting to half to see if that helps.


On the port that had 1,236,467 errors there were 1,105,155,612 transmitted bytes. Does that seem like a high amount of errors?

Thanks a bundle,

malaize2

 

[jneiberger]

That is a very low error rate and certainly not unusual for half duplex ethernet.

 

[voltron1011]

Devices plugged into a hub will be doing CSMA-CD to listen for collisions and find an opening to xmit, so it only makes sense that you will see this activity on your switch port.

 

[tharder]

Hubs = Collisions = Fragmented Packets
I agree with the previous posts. It's the ratio that's more important. If you have a handful of workstations that are heavy network users, expect a lot of collisions and performance to degrade rapidly for anyone else on the hub. Anything transmitted on the hub is sent to all ports....