service unsupported-transceiver

Some unsupported transceivers can be used in Cisco 3750. Obviously, Cisco wont support it!

c3750(config)#service unsupported-transceiver
 Warning: When Cisco determines that a fault or defect can be traced to
the use of third-party transceivers installed by a customer or reseller,
then, at Cisco's discretion, Cisco may withhold support under warranty or
a Cisco support program. In the course of providing support for a Cisco
networking product Cisco may require that the end user install Cisco
transceivers if Cisco determines that removing third-party parts will
assist Cisco in diagnosing the cause of a support issue.

c3750(config)#

Change MTU size in a 3750 port

The Catalyst 3750 cannot change the MTU per port. It can only be done globally in the switch with the command "system mtu 1526". For it to take effect you have to reload the switch.
10/100 ports: Max is 1998
1G: 9000 bytes



C3750#sh system mtu

System MTU size is 1524 bytes
System Jumbo MTU size is 1524 bytes
System Alternate MTU size is 1524 bytes
Routing MTU size is 1500 bytes

Unable to read configuration. Try again later.

CISCO6500#wr
Unable to read configuration. Try again later.

CISCO6500#


This is caused by high activity on CLI. Probably, a sh run is taking place or any other action that locks the executation of the CLI cmd.

high CPU usage on cisco catalyst 6500 with itasca process

In a Cisco 6500 switch with ACE, if the process itasca is consumming too much CPU, it can be caused by logging supervisor command on ACE.

This command will dump the logging of ACE into the supervisor and consumes RP resources.

To resolve this remove the cmd "logging supervisor " from ACE configuration and make ACE send the logging to a log server directly.
 
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The same problem was seen with logging generated by the switch itself.
The fix was: 
no logging on

At least, until the problem is found, the cpu was back to normal.

Before:
SWITCH# proc cpu sort
CPU utilization for five seconds: 99%/1%; one minute: 99%; five minutes: 99%
 PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
  62     2749624    243589      11287 86.82% 83.39% 84.82%   0 itasca
 131       11100     21481        516  0.47%  0.60%  0.67%   4 SSH Process
 499   5563701363409673472          0  0.39%  0.44%  0.45%   0 Port manager per
 
After: 
SWITCHh #sh proc cpu sort
CPU utilization for five seconds: 5%/1%; one minute: 9%; five minutes: 30%
 PID Runtime(ms)   Invoked      uSecs   5Sec   1Min   5Min TTY Process
 499   5563783763409717288          0  0.79%  0.94%  0.87%   0 Port manager per
 560     40374923186106614          1  0.31%  0.31%  0.31%   0 HSRP Common
 273   2786680721058539466        263  0.31%  0.36%  0.41%   0 IP Input