Setup Guide

95 Dell EMC PowerEdge MX SmartFabric Configuration and Troubleshooting Guide
12.2 Troubleshooting Spanning Tree Protocol (STP)
Spanning Tree Protocol (STP) prevents loops in the network. Loops can occur when multiple redundant parts
are available between the switches. To prevent the network from going down due to loops, various flavors of
STP are available. Initial introduction of STP evolved into various types. It is essential to ensure that network
loops are prevented by using appropriate type of STP on the upstream switches as well as the MX9116n
switches that are part of the MX SmartFabric.
12.2.1 Verify if STP is enabled on upstream switches
STP is required when connecting a SmartFabric to the upstream network. Turning off Spanning Tree in the
upstream switches will result in network loops and may cause downtime. Enable the appropriate STP type on
the upstream switches.
12.2.2 Verify if type of STP is the same on MX and upstream switches
Check the upstream switch if STP is enabled and verify that the type of STP matches the type of STP running
on the MX switches. By default, the MX switches run RPVST+ as shown below:
OS10# show spanning-tree brief
Spanning tree enabled protocol rapid-pvst
VLAN 1
Executing IEEE compatible Spanning Tree Protocol
---- OUTPUT TRUNCATED -----
The following example shows the STP on the upstream switches, Cisco Nexus 3232C, is configured to run
MST:
Nexus-3232C-Leaf1(config)# do show spanning-tree summary
Switch is in mst mode (IEEE Standard)
Root bridge for: MST0000
Port Type Default is disable
---- OUTPUT TRUNCATED -----
The recommended course of action is to change the STP type to RPVST+ on the upstream Cisco Nexus
switches.
Nexus-3232C-Leaf1(config)# spanning-tree mode rapid-pvst
Nexus-3232C-Leaf1(config)# do show spanning-tree summary
Switch is in rapid-pvst mode
---- OUTPUT TRUNCATED -----
Another course of action in the above case can be to change the spanning tree type on the MX switches
operating in SmartFabric mode to match the STP type on the upstream switches. This can be done using the
OS10EE CLI. The options available on the type of STP are as follows:
OS10(config)# spanning-tree mode ?
<rstp/mst/rapid-pvst> STP Protocol type
NOTE: MST is not currently supported in SmartFabric mode.