CCNA: PVST+ Load Sharing — Split VLANs Across Uplinks

Today's daily lab

Build a redundant campus triangle with two distribution switches and one access switch. Implement PVST+ per-VLAN root tuning so VLAN 10 forwards over DSW1 while VLAN 20 forwards over DSW2. Verify that each VLAN chooses a different root and that the blocked uplink differs per VLAN, while end hosts in each VLAN can still reach their local SVI gateway IP.

Learning objectives

• Configure 802.1Q trunks with hardened settings and consistent native VLAN across all inter-switch links
• Define and carry VLAN 10 and VLAN 20 throughout the triangle; place access ports in the correct VLANs
• Use PVST+ root tuning to make DSW1 the root for VLAN 10 and DSW2 the root for VLAN 20
• Confirm per-VLAN topology differences (root ports, designated ports, and blocked ports) with show commands
• Verify end-to-end reachability from hosts to their VLAN SVI across the redundant triangle

Troubleshooting focus

• If one VLAN forwards only via one uplink for all VLANs, verify the per-VLAN root settings on both distribution switches; each VLAN should have a different root.
• If a host cannot ping its SVI, confirm its access port VLAN, the VLAN’s existence on all three switches, and that all trunks allow that VLAN.
• If STP behavior is erratic, check for native VLAN mismatches and ensure nonegotiate is set on both sides of every trunk.
• If both VLANs show the access switch as the root, raise the access switch’s bridge priority so it cannot win the election.