Lab Objective
Change a switch's Spanning Tree mode from classic PVST+ to Rapid PVST+, verify the mode change took effect, and compare convergence time on a port before and after the change.
Lab Purpose
Classic 802.1D Spanning Tree, used by default in PVST+, takes up to 50 seconds to converge after a topology change, as observed in earlier labs. Rapid PVST+ (based on 802.1w) achieves convergence in seconds rather than tens of seconds, making it the standard choice in virtually all modern network deployments.
Lab Topology
Switch1 ---- Gi1/0/5 ---- Switch2
Switch1 ---- Gi1/0/6 ---- Switch2 (redundant link)
Both switches currently running default
PVST+ modeTask 1: Verify Current Spanning Tree Mode
Confirm both switches are currently running classic PVST+.
Task 2: Enable Rapid PVST+
Change the Spanning Tree mode to rapid-pvst on both switches.
Task 3: Verify the Mode Change
Confirm both switches now show rapid-pvst as the active mode.
Task 4: Compare Convergence Time
Shut down and re-enable the forwarding link, then time how quickly the blocking link transitions to forwarding, comparing this against the 30-50 second delay observed under classic PVST+ in an earlier lab.
Task 5: Observe Updated Port Role Terminology
Note any differences in how port roles are displayed under Rapid PVST+.
Solution and Verification
Switch1# show spanning-tree summary | include Mode
Spanning tree enabled protocol ieee
-- "ieee" indicates classic 802.1D PVST+Switch1(config)# spanning-tree mode rapid-pvst
Switch2(config)# spanning-tree mode rapid-pvstSwitch1# show spanning-tree summary | include Mode
Spanning tree enabled protocol rstp
-- Confirms Rapid PVST+ (based on RSTP, 802.1w)
-- is now activeSwitch1(config)# interface gigabitethernet1/0/5
Switch1(config-if)# shutdown
Switch1(config-if)# no shutdown
Switch1# show spanning-tree vlan 1
-- checked repeatedly: the previously blocking
-- link (Gi1/0/6) transitions to forwarding
-- within roughly 1-6 seconds, dramatically
-- faster than the 30-50 seconds observed
-- under classic PVST+ in the earlier root
-- bridge labSwitch1# show spanning-tree vlan 1
Interface Role Sts Cost Prio.Nbr Type
Gi1/0/5 Desg FWD 4 128.5 P2p
Gi1/0/6 Root FWD 4 128.6 P2p
-- Notice the port role naming remains
-- consistent (Root, Designated, Alternate),
-- though RSTP's internal state machine that
-- achieves this transition so quickly is
-- fundamentally different from classic STPKey Takeaway
Rapid PVST+ dramatically reduces convergence time compared to classic PVST+ while keeping the same familiar per-VLAN priority and port role concepts covered in earlier labs — this makes migrating an existing PVST+ network to Rapid PVST+ a low-risk, high-value change, since it is largely a mode switch rather than a redesign of the underlying VLAN and priority configuration.