Spanning-Tree Backbonefast Command on CISCO Router/Switch

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)#

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