STP

Spanning Tree Protocol

Wiki Reference

AlliedWare Reference

Ref: H3C STP

Ref: Arista STP with Cisco

• STP (Spanning Tree Protocol) / CST (Common Spanning Tree)
  • IEEE 802.1D
• RSTP (Rapid Spanning Tree Protocol)
  • IEEE 802.1w
  • Compatible with CST
• MSTP (Multiple Spanning Tree Protocol)
  • IEEE 802.1s, IEEE 802.1Q-2005
• PVST (Per-VLAN Spanning Tree)
  • Cisco proprietary protocol
  • PVST = CST BPDU on native VLAN + SSTP per VLAN
• Rapid-PVST
  • Cisco proprietary protocol
  • Compatible with PVST

Port role	Forward BPDU	Forward frame
Root	X	O
Blocked / Alternate	X	X
Designated	O	O

STP mode

Switch(config)# spanning-tree mode { pvst | rapid-pvst | mst }

Root guard

If a root guard enabled port receives superior STP BPDU, root guard moves this port to a root-inconsistent (listening) state.

Switch(config-if)# spanning-tree guard root

Loop guard

Reference

If a non-designated port no longer receive STP BPDU, the port transitions into loop-inconsistent (blocking) state.

Switch(config-if)# spanning-tree guard loop

Enable loop guard on all port

Switch(config)# spanning-tree loopguard default

Port fast

Immediately brings interface to the forwarding state from a blocking state

Switch(config-if)# spanning-tree portfast [disable]

Enable port fast on all access port

Switch(config)# spanning-tree portfast default

BPDU guard

If BPDU is detected on the port, the port will be err-disable.

Switch(config-if)# spanning-tree bpduguard { enable | disable }

Enable BPDU guard on all port fast port

Switch(config)# spanning-tree portfast bpduguard default

BPDU filter

Ignore BPDU

Switch(config-if)# spanning-tree bpdufilter { enable | disable }