2In−Discard and Lrn−Discard do not exist on all Catalyst platforms.
Table 5Possible Causes for Incrementing CatOS Counters
Counter | Possible Cause |
| |
Delay Exced | Severe problem with the switch. Create a service |
| request with Cisco Technical Support. |
|
|
| Verify ISL and dot1q configurations. Verify |
MTU−Exced | another switch or router does not inject frame |
| over maximum transmission unit (MTU) into the |
| switch network. |
|
|
| Increments when the switch receives traffic on a |
Lrn−Discard | trunk for a specific VLAN while the switch does |
2 | not have any other ports on that VLAN. Counter |
| |
| also increments when the destination address of |
| the packet is learned on the port on which the |
| packet is received. |
|
|
Lrn−Discard | This counter must remain at zero. If counter |
2 | |
| increments, create a service request with Cisco |
| Technical Support. |
In−Lost | Excessive input rate of traffic. |
| |
| Excessive output rate of traffic. Increments in this |
| counter are more likely to occur when connected |
Out−Lost | to low−speed devices. The first step to |
| troubleshoot Out−Lost increments is to verify the |
| link partner runs 100 Mbps, full−duplex without |
| any errors. |
|
|
2In−Discard and Lrn−Discard do not exist on all Catalyst platforms.
Additional counter information can be viewed with the command show counters mod/port . The command must be issued for a single port at a time. Refer to this document for information on the counter displayed:
∙show counters Command Documentation
For additional information about the Cisco IOS Software show interfaces command counters, refer to:
∙show interfaces Command Documentation
Sniffer Trace
Sniffer trace analysis can be very useful when you troubleshoot switch and NIC performance or connectivity issues when the issues persist after all other sections of this document are reviewed. Sniffer trace analysis reveals every packet on the wire and pinpoints the exact problem. It can be important to obtain several sniffer traces from different ports on different switches. Generally, it is very useful to monitor or span ports rather than spanning VLANs when you troubleshoot switch and NIC performance and connectivity issues.
Refer to Catalyst Switched Port Analyzer (SPAN) Configuration Example for more information on the use of the Switched Port Analyzer (SPAN) feature required to obtain sniffer traces.