Verifying The Stp Extension Configuration; Troubleshooting Loop Detection Error Message - Cisco Nexus 3000 Series Configuration Manual
Nx-os layer 2 switching configuration
guide, release 6.x
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Also See for Nexus 3000 Series:
- Command reference manual (356 pages) ,
- Configuration manual (338 pages) ,
- Installation manual (112 pages)
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Verifying the STP Extension Configuration
This example shows how to enable Root Guard on Ethernet port 1/4:
switch# configure terminal
switch (config)# interface ethernet 1/4
switch(config-if)# spanning-tree guard root
Verifying the STP Extension Configuration
Use the following commands to display the configuration information for the STP extensions.
Command
show running-config spanning-tree [all]
show spanning-tree [options]
Troubleshooting Loop Detection Error Message
This section describes how to address the FWM-2-STM_LOOP_DETECT error message in the log of Cisco
Nexus 3000 Series switches.
If the Cisco Nexus 3000 Series switch displays the following message, it indicates that the switch receives
frames with the same source MAC address on these two interfaces and that the switch learns the same MAC
address on these interfaces at a very high speed. The switch detects this condition as a loop. The switch disables
the MAC address learning in order to protect its control plane. It is implemented on all VLANs even if the
loop occurs on only one VLAN.
2016 Apr 11 18:00:18 N3k-4-3229 %FWM-2-STM_LOOP_DETECT: Loops detected in the network for
mac 0000.0602.0602 among ports Eth1/48
and Eth1/50/3 on vlan 4 - Disabling dynamic learning notifications for a period between 120
and 240 seconds on vlan 4
The possible causes of the error message are:
• MAC addresses move because of incorrect Spanning Tree Protocol (STP)-port state convergence.
• MAC addresses move because the source of the data is physically moved across all switches while STP
Detecting the Loop
The Forwarding Manager (FWM) has a mechanism to count the number of moved MAC addresses and weigh
them based on the number of times the MAC address moves. It determines the total count (switch-wide across
all VLANs, MACs, and interfaces) of the moved MAC addresses, declares the
%FWM-2-STM_LOOP_DETECT condition, and disables learning to protect FWM in loop conditions.
Note
MAC learning is disabled per VLAN and not per system.
Cisco Nexus 3000 Series NX-OS Layer 2 Switching Configuration Guide, Release 6.x
116
states are converged and in correct states.
Configuring STP Extensions
Purpose
Displays the current status of spanning tree on the
switch.
Displays selected detailed information for the current
spanning tree configuration.
OL-29545-03
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