Comware

I have a stack of 7 (dont ask) 3Com 5500's and periodically i am seeing a high number of CPU cycles being hit by these switches handling various servers hanging off these units.



Can anyone tell me if there is a document (and dont just paste the CLI guide reference, ive been through it) that tells you how you can track down the traffic that is causing this pattern or even what process the switch goes through in the decision making pcocess as to whether to switch the packets in dedicated hardware (ASIC/MIPS) or to use the CPU instead.



Any advice would be greatfully recieved.

Hi kjones1,

I have similar problem. I have a stack of 2 3COM 5500G's. I already tried to separate them into 2 separate unit. And change the switch configuration to factory default. I also removed all UTP cables from those switches. I only use console cable to connect to one of the switches.

The problem is, if i put "dis cpu" command repeatly to the switch, the 5 second cpu process increase from 20% to 60%. I already upgraded the flash to the latest flash.

Have you solved your problem? Could you share it to me?

Regards...

 

Usually the 5500G-EI switches presents the CPU utilization around 20 to 55%. It sounds weird at a first sight, but this is the normal range that I have been checking in 3 years that I've been working with these switches. When stacked, the units of the stack are constantly exchanging informations concerning routing and switching tables, and normally shows a CPU around 50~55%, with peaks of 60~70% of usage.





The memory usage is a better reference to check if there are spurious traffic in the environment, because does not show more than 20~30% at normal utilization levels.

Instead other vendors, these levels of CPU does not represents high utilization, but if these levels pass from 70~80% for more than 5 minutes then you have a problem.

Hi Fred,

Could you tell me command that you are using to show memory usage?

And could you tell me default function that i should remove to reduce CPU utilization below 20%?

Thanks,

 

 

To see the memory usage the command is display memory. To reduce the CPU utilization to 20%, there is no way...unless you don't use it's Layer 3 features and keep it almost the default configuration. But I don't think that the switch will remain in this usage low level.

Don't worry about it, it's normal and even if the switch reaches higher levels in traffic at L2/L3 the CPU normally doesn't pass from 60% or 70%. I already saw stacked 5500G switches working normally with medium size networks at 60%~70% of CPU, without any problem of performance or unstability.

Regards

Hi Fred,

I attach my switch 5500 back to my network. When i see the memory of switch 5500, the memory usage is 54%. Is it normal or not? By the way, have you tried to use snmp or snmp trap to get information about error in the network? Because it's hard to know what is the problem that occur in my network.

Regards,

 

Yes, it's normal. Even when mounting a stack right out of the box the usage levels are these. I really don't think that is something wrong in your environment since all the stacks I've configured have showed the same statistics.

Regards

Hi Fred,

Have you tried to connect your 3COM 5500 with switches from other brand? For example Cisco, Nortel, or Foundry? Have you experienced with High CPU utilization problem in 3COM 5500 after you connect with them? What should you disable in 3COM 5500? Should you disable cluster setting (NDB) from your 3COM 5500?

Regards,