zNetLaB › Guided labs › Enterprise
MST — one region, two instances, forty VLANs
Enterprise Advanced 3 devices 5 checked tasks 100 points Plan lab
PVST+ runs one tree per VLAN, which is forty trees for forty VLANs. Put all three switches in one MST region, map the VLANs into two instances, and make a different switch root for each — the same load balancing, two elections instead of forty. 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
PVST+ runs one tree per VLAN, which is forty trees for forty VLANs. Put all three switches in one MST region, map the VLANs into two instances, and make a different switch root for each — the same load balancing, two elections instead of forty.
Your role: a network engineer on the enterprise team. Level: Advanced Done when: all 5 goals show as passed (100 points).
Network status
Devices: 3 switchs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. SW1 starts with and VLAN 10, VLAN 20, VLAN 30, VLAN 40 already configured. SW2 starts with and VLAN 10, VLAN 20, VLAN 30, VLAN 40 already configured. SW3 starts with and VLAN 10, VLAN 20, VLAN 30, VLAN 40 already configured. 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
All three switches run MST (15 pts) Instance 1 carries VLANs 10 and 20 on every switch (20 pts) Instance 2 carries VLANs 30 and 40 on every switch (20 pts) SW1 is root for instance 1 and SW2 for instance 2 (25 pts) A VLAN 10 frame and a VLAN 30 frame take different paths (20 pts) The activity, in order
All three switches run MST Why: Every switch in a domain must run the same mode or the topology will not converge as designed. Verify with: show spanning-tree summary Instance 1 carries VLANs 10 and 20 on every switch Why: Each goal is a state the lab can check on the running device. Verify with: show running-config Instance 2 carries VLANs 30 and 40 on every switch Why: Each goal is a state the lab can check on the running device. Verify with: show running-config SW1 is root for instance 1 and SW2 for instance 2 Why: Each goal is a state the lab can check on the running device. Verify with: show running-config A VLAN 10 frame and a VLAN 30 frame take different paths Why: Each goal is a state the lab can check on the running device. Verify with: show running-config 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
PVST+ runs one tree per VLAN, which is forty trees for forty VLANs. Put all three switches in one MST region, map the VLANs into two instances, and make a different switch root for each — the same load balancing, two elections instead of forty.
What you will be able to do
All three switches run MST
Instance 1 carries VLANs 10 and 20 on every switch
Instance 2 carries VLANs 30 and 40 on every switch
SW1 is root for instance 1 and SW2 for instance 2
The network
Catalyst 9300-24 — 3 devices in all, already cabled.
Gi1/0/1 Gi1/0/1 Gi1/0/2 Gi1/0/2 Gi1/0/3 Gi1/0/3 SW1 SW2 SW3 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
SW1 Catalyst 9300-24 configure it SW2 Catalyst 9300-24 configure it SW3 Catalyst 9300-24 configure it
Cabling
SW1 Gi1/0/1 ↔ SW2 Gi1/0/1 SW1 Gi1/0/2 ↔ SW3 Gi1/0/2 SW2 Gi1/0/3 ↔ SW3 Gi1/0/3
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
SW1 vlan 10
exit
vlan 20
exit
vlan 30
exit
vlan 40
exit
interface range GigabitEthernet1/0/1 - 3
switchport trunk encapsulation dot1q
switchport mode trunk
exit SW2 vlan 10
exit
vlan 20
exit
vlan 30
exit
vlan 40
exit
interface range GigabitEthernet1/0/1 - 3
switchport trunk encapsulation dot1q
switchport mode trunk
exit SW3 vlan 10
exit
vlan 20
exit
vlan 30
exit
vlan 40
exit
interface range GigabitEthernet1/0/1 - 3
switchport trunk encapsulation dot1q
switchport mode trunk
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 All three switches run MST 15 Checked automatically against the device’s live state (stpMode). and Checked automatically against the device’s live state (stpMode). and Checked automatically against the device’s live state (stpMode). 2 Instance 1 carries VLANs 10 and 20 on every switch 20 Checked automatically against the device’s live state (mstMaps). and Checked automatically against the device’s live state (mstMaps). and Checked automatically against the device’s live state (mstMaps). 3 Instance 2 carries VLANs 30 and 40 on every switch 20 Checked automatically against the device’s live state (mstMaps). and Checked automatically against the device’s live state (mstMaps). and Checked automatically against the device’s live state (mstMaps). 4 SW1 is root for instance 1 and SW2 for instance 2 25 Checked automatically against the device’s live state (stpRootFor). and Checked automatically against the device’s live state (stpRootFor). 5 A VLAN 10 frame and a VLAN 30 frame take different paths 20 Checked automatically against the device’s live state (vlanBlocks). and Checked automatically against the device’s live state (vlanForwards). and Checked automatically against the device’s live state (vlanBlocks). and Checked automatically against the device’s live state (vlanForwards).
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:
SW1 spanning-tree mode mst
spanning-tree mst configuration
name CAMPUS
revision 1
instance 1 vlan 10,20
instance 2 vlan 30,40
exit
spanning-tree mst 1 priority 4096 SW2 spanning-tree mode mst
spanning-tree mst configuration
name CAMPUS
revision 1
instance 1 vlan 10,20
instance 2 vlan 30,40
exit
spanning-tree mst 2 priority 4096 SW3 spanning-tree mode mst
spanning-tree mst configuration
name CAMPUS
revision 1
instance 1 vlan 10,20
instance 2 vlan 30,40
exit
spanning-tree mst 1 priority 61440
spanning-tree mst 2 priority 61440 Where this is examined
This lab practises these topics in the zNetLaB certification courses:
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