Showing results for 
Search instead for 
Did you mean: 

Packets larger than a certain size can be dropped by a Catalyst 4000 / 4500 series switch that runs Cisco IOS system software


Core issue

The devices that are connected to a Catalyst 4000 or 4500 series switch can sometimes experience poor network connectivity. Some packets are dropped by the switch due to a faulty Static RAM (SRAM) component on the Supervisor Engine. Larger packets are affected more than smaller ones. The transient SRAM failure is rare and is seen on only a small number of Supervisor Engines. A similar problem is identified on Catalyst 4000 Supervisor Engine 2.

Refer to Cisco bug ID CSCdz57255 for more information on this issue.


In order to resolve this issue, upgrade to Cisco IOS  Software Release 12.2(18)SXF4 or later, which can be downloaded from the LAN Switching Software page.

For Cisco IOS software releases earlier than 12.1(19)EW, the workaround is to power it off and on in order to hard reset the switch.

For Cisco IOS Software Release 12.1(19)EW or later but earlier than Cisco IOS Software Release 12.2(18)EW, the SRAM workaround incorporated is partial.

For Cisco IOS Software Release 12.1(21)E and earlier, the SRAM workaround is partial too. The software detects, logs and takes appropriate action, which depends upon the configuration mode. The SRAM workaround can be configured in either of these three modes:

  • normal  
  • conservative  
  • aggressive

Use the diagnostic monitor action [conservative | normal | aggressive] command in order to set the mode.

Open a case with Cisco Technical Support with the TAC Service Request Tool for more assistance and support.