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2
In−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.
MTU−Exced
Verify ISL and dot1q configurations. Verify
another switch or router does not inject frame
over maximum transmission unit (MTU) into the
switch network.
Lrn−Discard
2
Increments when the switch receives traffic on a
trunk for a specific VLAN while the switch does
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
2
This counter must remain at zero. If counter
increments, create a service request with Cisco
Technical Support.
In−Lost
Excessive input rate of traffic.
Out−Lost
Excessive output rate of traffic. Increments in this
counter are more likely to occur when connected
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.
2
In−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.