Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual page 44

Chapter 3 Troubleshooting Layer 2 Switching Issues
MAC Address Table
S e n d d o c u m e n t c o m m e n t s t o n e x u s 5 k - d o c f e e d b a c k @ c i s c o . c o m .
After waiting for 180 seconds, the MAC table is flushed and learning is enabled automatically.
Alternatively, wait until some MAC entries are aged out, so that the total learned entries fall below 1500,
or enter the clear mac address-table dynamic [address <mac>] command to clear out entries. This
creates free space for new MAC entries to be learned. A severity 2 syslog message,
STM_LEARNING_RE_ENABLE, should be received.
Possible Cause
MAC address learning is disabled due to a learning overload (that is, too many new addresses in a short
time). A severity 4 syslog message, STM_LEARNING_OVERLOAD, should have been received.
Solution
After waiting for 120 seconds, learning is enabled automatically.
MAC address not learned
MAC address is not learned by the switch. This causes the MAC address not to be listed in the MAC
table.
Possible Cause
MAC address learning is disabled because of loop detection. A severity 2 syslog message,
STM_LOOP_DETECT, should have been received.
Solution
After waiting for 180 seconds, learning is enabled automatically. A severity 2 syslog message,
STM_LEARNING_RE_ENABLE, should be received.
Possible Cause
The MAC address table is full. A severity 2 syslog message, STM_LIMIT_REACHED, should have been
received.
Solution
After waiting for 180 seconds, the MAC table is flushed and learning is enabled automatically.
Alternatively, wait until some MAC entries are aged out, so that the total learned entries fall below 1500,
or enter the clear mac address-table dynamic [address <mac>] command to clear out entries. This
creates free space for new MAC entries to be learned. A severity 2 syslog message,
STM_LEARNING_RE_ENABLE, should be received.
Possible Cause
MAC address learning is disabled due to a learning overload (that is, too many new addresses in a short
time). A severity 4 syslog message, STM_LEARNING_OVERLOAD, should have been received.
Solution
After waiting for 120 seconds, learning is enabled automatically.
Possible Cause
No egress path was set for the incoming data traffic. The MAC address from a data stream is not learned
if there is no path for that data going out of the switch.
Solution
Configure an outgoing path for the data.
For example, the VLAN may not have been enabled on any of the interfaces other than the one on which
data is coming in on. Alternatively, the outgoing interfaces may be down. If this is the case, you need to
bring up those interfaces.
Cisco Nexus 5000 Series Troubleshooting Guide
3-2
OL-25300-01