When using the legacy Ethernet uplink type, it is essential to ensure that network loops are prevented by using appropriate Spanning Tree Protocol (STP) on the MX and upstream switches. 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 types of STP are available.
When using the Ethernet – No Spanning Tree Protocol uplink, STP is not required on the upstream switch interfaces.
spanning-tree {vlan vlan-id priority priority-value}
. Set the external switch to the lowest priority-value to force its assignment as the STP root bridge. For additional details on using STP with OS10 switches, see the Dell OS10 SmartFabric User Guide. Verify STP is enabled on upstream switches
STP is required when connecting a SmartFabric to the upstream network when using the legacy Ethernet uplink. 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.
Verify STP type is identical 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 that 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. Make the change using the SmartFabric OS10 CLI. The options available for the type of STP are as follows:
MX9116N-A1(config)# spanning-tree mode ?
rstp Enable rstp
rapid-pvst Enable rapid-pvst