Troubleshooting Layer 2 Switching Issues; Mac Address Table - Cisco N5K-M1600 - Expansion Module - 6 Ports Troubleshooting Manual

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 .

Troubleshooting Layer 2 Switching Issues

Layer 2 is the Data Link Layer of the Open Systems Interconnection model (OSI model) of computer
networking.
This chapter describes how to identify and resolve problems that can occur with Layer 2 switching in
the Cisco Nexus 5000 Series switch.
This chapter includes the following sections:
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MAC Address Table

Data traffic is flooding
Data is not getting forwarded, instead it is being flooded to all ports of a VLAN.
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
OL-25300-01
MAC Address Table
Spanning Tree Protocol
Multicast
VLANs
Registers and Counters
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C H A P T E R
Cisco Nexus 5000 Series Troubleshooting Guide
3-1