See how switches elect a root bridge, select port roles, block redundant paths, and reconverge when the topology changes. Explore three VLAN instances on a four-switch campus mesh with authentic IOS output.
Solid green = forwarding tree. Dashed / hatched = discarding alternate. Keyboard: Tab to links and switches, Enter to select.
When Rapid PVST+ starts on a VLAN, each switch begins by advertising itself as the root bridge with bridge ID (priority + VLAN extended system ID).MAC.
| Switch port | VLAN 10 | VLAN 20 | VLAN 30 |
|---|---|---|---|
| ACCESS1 Gi0/1 | Root/FWD | Root/FWD | Root/FWD |
| ACCESS1 Gi0/2 | Altn/BLK | Altn/BLK | Altn/BLK |
| ACCESS2 Gi0/1 | Root/FWD | Root/FWD | Root/FWD |
| ACCESS2 Gi0/2 | Altn/BLK | Altn/BLK | Altn/BLK |
| DIST1 Gi0/1 | Desg/FWD | Desg/FWD | Desg/FWD |
| DIST1 Gi0/2 | Desg/FWD | Desg/FWD | Desg/FWD |
| DIST1 Gi0/3 | Desg/FWD | Desg/FWD | Desg/FWD |
| DIST2 Gi0/1 | Root/FWD | Root/FWD | Root/FWD |
| DIST2 Gi0/2 | Desg/FWD | Desg/FWD | Desg/FWD |
| DIST2 Gi0/3 | Desg/FWD | Desg/FWD | Desg/FWD |
VLAN10 is executing the rstp compatible Spanning Tree protocol
Bridge ID Priority 32778
Address 0001.0001.0001
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Root ID Priority 32778
Address 0001
Cost 0
Port 0
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- -------- -------- ----
Gi0/1 Desg FWD 4 128 1 P2p
Gi0/2 Desg FWD 4 128 2 P2p| Feature | Purpose | Common misconfig |
|---|---|---|
| PortFast | Fast transition for host ports | Enabled on switch-to-switch links |
| BPDU Guard | Protect PortFast ports from rogue switches | Disabled globally on access switches |
| Root Guard | Block superior root BPDUs on designated ports | Confused with BPDU Guard |
| Loop Guard | Block when BPDUs are lost on non-designated ports | Used instead of Root Guard |
Classic 802.1D used blocking, listening, learning, forwarding, and disabled. Rapid STP (RSTP) uses discarding, learning, and forwarding. This lab models Rapid PVST+ behavior.