It is not recommended to use the legacy Ethernet uplink type when creating a new SmartFabric. Use the Ethernet - No Spanning Tree uplink.
By default, SmartFabric OS10 uses Rapid per-VLAN Spanning Tree Plus (RPVST+) across all switching platforms including PowerEdge MX networking IOMs. SmartFabric OS10 also supports RSTP.
Caution should be taken when connecting an RPVST+ to an existing RSTP environment. RPVST+ creates a single topology per VLAN with the default VLAN, typically VLAN 1, for the Common Spanning Tree (CST) with RSTP.
For non-native VLANs, all bridge protocol data unit (BPDU) traffic is tagged and forwarded by the upstream, RSTP-enabled switch with the associated VLAN. These BPDUs use a protocol-specific multicast address.
Any other RPVST+ tree that is attached to the RSTP tree might process these packets accordingly leading to the potential of unexpected trees.
To switch from RPVST+ to RSTP, use the spanning-tree mode rstp command:
MX9116N-A1(config)# spanning-tree mode rstp
MX9116N-A1(config)# end
To validate the STP configuration, use the show spanning-tree brief command:
MX9116N-A1#show spanning-tree brief
Spanning tree enabled protocol rstp with force-version rstp
Executing IEEE compatible Spanning Tree Protocol Root ID Priority 0, Address 4c76.25e8.f2c0 Root Bridge hello time 2, max age 20, forward delay 15 Bridge ID Priority 32768, Address 2004.0f00.cd1e Configured hello time 2, max age 20, forward delay 15 Flush Interval 200 centi-sec, Flush Invocations 95 Flush Indication threshold 0 (MAC flush optimization is disabled)
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.