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Per-VLAN spanning tree — two VLANs, two roots
Enterprise Intermediate 5 devices 6 checked tasks 100 points Plan lab
Two uplinks, two VLANs, and one of the uplinks idle. Make DSW1 the root for VLAN 10 and DSW2 the root for VLAN 20, then prove a DIFFERENT port blocks in each — which is the whole reason PVST+ exists and the only way both uplinks carry traffic. You build it in a browser, type real commands at each device, and every task below is
checked against the running configuration — so you find out it is wrong before anybody else does.
Open this lab in the simulator
The simulator runs in your browser with nothing to install. This lab is part of the full simulator: open it free for 7 days with a new account, then with a plan. It needs an account, which keeps your progress.
The scenario
Two uplinks, two VLANs, and one of the uplinks idle. Make DSW1 the root for VLAN 10 and DSW2 the root for VLAN 20, then prove a DIFFERENT port blocks in each — which is the whole reason PVST+ exists and the only way both uplinks carry traffic.
Your role: a network engineer on the enterprise team. Level: Intermediate Done when: all 6 goals show as passed (100 points).
Network status
Devices: 3 switchs, 2 PCs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. DSW1 starts with and VLAN 10, VLAN 20 already configured. DSW2 starts with and VLAN 10, VLAN 20 already configured. ASW1 starts with and VLAN 10, VLAN 20 already configured. PC-Sales is a host with 10.10.10.10/24. PC-Eng is a host with 10.10.20.10/24. Known problems
None: nothing is misconfigured. The network is simply not finished: what the goals list is what you have to build or secure. Goals
DSW1 is the root bridge for VLAN 10 (20 pts) DSW2 is the root bridge for VLAN 20 (20 pts) …and neither is root for the other’s VLAN (15 pts) On ASW1 the VLAN 10 tree blocks the DSW2 uplink (20 pts) …and the VLAN 20 tree blocks the DSW1 uplink instead (20 pts) Both hosts still reach their own gateway subnet (5 pts) The activity, in order
DSW1 is the root bridge for VLAN 10 Why: Each goal is a state the lab can check on the running device. Verify with: show running-config DSW2 is the root bridge for VLAN 20 Why: Each goal is a state the lab can check on the running device. Verify with: show running-config …and neither is root for the other’s VLAN Why: Each goal is a state the lab can check on the running device. Verify with: show running-config On ASW1 the VLAN 10 tree blocks the DSW2 uplink Why: Each goal is a state the lab can check on the running device. Verify with: show running-config …and the VLAN 20 tree blocks the DSW1 uplink instead Why: Each goal is a state the lab can check on the running device. Verify with: show running-config Both hosts still reach their own gateway subnet Why: A VLAN is a separate broadcast domain; the port’s VLAN decides which devices can talk without a router. Verify with: show vlan brief Tips
Work in the order given: later goals depend on the earlier ones. After every change, run the verify command before moving on; do not guess. Stuck? Read the verify output first. It names the interface, neighbour or route that is wrong. Why this matters
Two uplinks, two VLANs, and one of the uplinks idle. Make DSW1 the root for VLAN 10 and DSW2 the root for VLAN 20, then prove a DIFFERENT port blocks in each — which is the whole reason PVST+ exists and the only way both uplinks carry traffic.
What you will be able to do
DSW1 is the root bridge for VLAN 10
DSW2 is the root bridge for VLAN 20
…and neither is root for the other’s VLAN
On ASW1 the VLAN 10 tree blocks the DSW2 uplink
The network
Catalyst 9300-24, Catalyst 2960-24TT, PC — 5 devices in all, already cabled.
Gi1/0/1 Gi1/0/1 Gi1/0/2 Fa0/1 Gi1/0/2 Fa0/2 Fa0/10 Fa0 Fa0/20 Fa0 DSW1 DSW2 ASW1 PC-Sales 10.10.10.10/24 PC-Eng 10.10.20.10/24 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
DSW1 Catalyst 9300-24 configure it DSW2 Catalyst 9300-24 configure it ASW1 Catalyst 2960-24TT configure it PC-Sales PC 10.10.10.10 / 255.255.255.0 PC-Eng PC 10.10.20.10 / 255.255.255.0
Cabling
DSW1 Gi1/0/1 ↔ DSW2 Gi1/0/1 DSW1 Gi1/0/2 ↔ ASW1 Fa0/1 DSW2 Gi1/0/2 ↔ ASW1 Fa0/2 ASW1 Fa0/10 ↔ PC-Sales Fa0 ASW1 Fa0/20 ↔ PC-Eng Fa0
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
DSW1 vlan 10
name SALES
exit
vlan 20
name ENG
exit
interface range GigabitEthernet1/0/1 - 2
switchport trunk encapsulation dot1q
switchport mode trunk
exit DSW2 vlan 10
name SALES
exit
vlan 20
name ENG
exit
interface range GigabitEthernet1/0/1 - 2
switchport trunk encapsulation dot1q
switchport mode trunk
exit ASW1 vlan 10
name SALES
exit
vlan 20
name ENG
exit
interface range FastEthernet0/1 - 2
switchport mode trunk
exit
interface FastEthernet0/10
switchport mode access
switchport access vlan 10
exit
interface FastEthernet0/20
switchport mode access
switchport access vlan 20
exit Tasks, and how each one is checked
Every task is decided by reading the live network — a neighbour in FULL, a ping that succeeds, a line in the running configuration — not by looking for a keyword you typed. The same command shows you what the lab sees.
# Task Pts How to verify it yourself
1 DSW1 is the root bridge for VLAN 10 20 Checked automatically against the device’s live state (stpRootFor). 2 DSW2 is the root bridge for VLAN 20 20 Checked automatically against the device’s live state (stpRootFor). 3 …and neither is root for the other’s VLAN 15 Checked automatically against the device’s live state (stpRootFor). and Checked automatically against the device’s live state (stpForwards). and Checked automatically against the device’s live state (stpForwards). 4 On ASW1 the VLAN 10 tree blocks the DSW2 uplink 20 Checked automatically against the device’s live state (stpBlocks). 5 …and the VLAN 20 tree blocks the DSW1 uplink instead 20 Checked automatically against the device’s live state (stpBlocks). 6 Both hosts still reach their own gateway subnet 5 On ASW1: show vlan brief — Fa0/10 is an access port in VLAN 10. and On ASW1: show vlan brief — Fa0/20 is an access port in VLAN 20.
Stuck? Ask the coach
Tell the coach what you see or what you tried. It gives you a hint, not the answer, the way a senior engineer would. Included with a free trial or any plan.
Ask the coach
Reference solution
Try it yourself first — the lab checks your work either way. This is one configuration that makes every task pass, device by device:
DSW1 spanning-tree vlan 10 priority 4096
spanning-tree vlan 20 priority 20480 DSW2 spanning-tree vlan 20 priority 4096
spanning-tree vlan 10 priority 20480 Where this is examined
This lab practises these topics in the zNetLaB certification courses:
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