Command
Spanning-Tree Backbonefast
Use
This command will prevent a switch that has lost its link to the root switch from becoming root when the root is still running. If switches receive an inferior BPDU from a switch, backbonefast will send them the proper information for reaching the root.
Syntax
Switch(config)#spanning-tree backbonefast
Example
In the below example we will configure backbonefast on all switches. After several link failures, we can see that SW4 is correcting SW2’s BPDUs.
SW1(config)#spanning vlan 1-4094 root primary SW1(config)#spanning backbonefast
SW4(config-if-range)#do show spanning back BackboneFast is enabled BackboneFast statistics ———————– Number of transition via backboneFast (all VLANs) : 12 Number of inferior BPDUs received (all VLANs) : 99 Number of RLQ request PDUs received (all VLANs) : 153 Number of RLQ response PDUs received (all VLANs) : 60 Number of RLQ request PDUs sent (all VLANs) : 245 Number of RLQ response PDUs sent (all VLANs) : 93 SW4(config-if-range)#