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Router on a stick 57 — VLANs 42 and 43
Enterprise Intermediate 4 devices 4 checked tasks 100 points Plan lab
Faculty (VLAN 42) and Engineering (VLAN 43) sit on one switch and must reach each other through one router port. Trunk the switch uplink, create the two 802.1Q sub-interfaces on the router (gateways .1 of 192.168.76.0/24 and 192.168.176.0/24), and ping between the departments. 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
Faculty (VLAN 42) and Engineering (VLAN 43) sit on one switch and must reach each other through one router port. Trunk the switch uplink, create the two 802.1Q sub-interfaces on the router (gateways .1 of 192.168.76.0/24 and 192.168.176.0/24), and ping between the departments.
Your role: a network engineer on the enterprise team. Level: Intermediate Done when: all 4 goals show as passed (100 points).
Network status
Devices: 1 router, 1 switch, 2 PCs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. SW-Nellore starts with and VLAN 42, VLAN 43 already configured. Faculty-PC is a host with 192.168.76.10/24, gateway 192.168.76.1. Engineering-PC is a host with 192.168.176.10/24, gateway 192.168.176.1. R-Nellore starts with an empty configuration. 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
The switch uplink Gi0/1 is a trunk (25 pts) Sub-interface Gi0/0.42 uses dot1Q 42 and is the gateway of Faculty (25 pts) Sub-interface Gi0/0.43 uses dot1Q 43 and is the gateway of Engineering (25 pts) Faculty reaches Engineering (25 pts) The activity, in order
The switch uplink Gi0/1 is a trunk Why: A trunk carries many VLANs over one cable, tagged with 802.1Q. Both ends must agree. Verify with: show interfaces trunk Sub-interface Gi0/0.42 uses dot1Q 42 and is the gateway of Faculty Why: This is the task that checks your configuration directly: the line must really be there, not just look right. Verify with: show running-config Sub-interface Gi0/0.43 uses dot1Q 43 and is the gateway of Engineering Why: This is the task that checks your configuration directly: the line must really be there, not just look right. Verify with: show running-config Faculty reaches Engineering Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 192.168.176.10 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. Common mistake: Forgetting no shutdown on the physical interface Common mistake: Sub-interface number and dot1Q id that disagree Common mistake: Trunk allowed list missing a VLAN Why this matters
Hosts in different VLANs are in different subnets, so they need a router. One physical router port carries them all as an 802.1Q trunk with a sub-interface per VLAN — the classic router on a stick.
What you will be able to do
Configure an 802.1Q trunk
Create sub-interfaces with encapsulation dot1Q
Explain inter-VLAN routing
The network
ISR 2911, Catalyst 2960-24TT, PC — 4 devices in all, already cabled.
Gi0/0 Gi0/1 Fa0/1 Fa0 Fa0/2 Fa0 R-Nellore SW-Nellore Faculty-PC 192.168.76.10/24 · gw 192.168.76.1 Engineering-PC 192.168.176.10/24 · gw 192.168.176.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
R-Nellore ISR 2911 configure it SW-Nellore Catalyst 2960-24TT configure it Faculty-PC PC 192.168.76.10 / 255.255.255.0 gw 192.168.76.1 Engineering-PC PC 192.168.176.10 / 255.255.255.0 gw 192.168.176.1
Cabling
R-Nellore Gi0/0 ↔ SW-Nellore Gi0/1 SW-Nellore Fa0/1 ↔ Faculty-PC Fa0 SW-Nellore Fa0/2 ↔ Engineering-PC 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:
SW-Nellore vlan 42
exit
vlan 43
exit
interface fa0/1
switchport mode access
switchport access vlan 42
exit
interface fa0/2
switchport mode access
switchport access vlan 43
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 The switch uplink Gi0/1 is a trunk 25 On SW-Nellore: show interfaces trunk lists Gi0/1. 2 Sub-interface Gi0/0.42 uses dot1Q 42 and is the gateway of Faculty 25 On R-Nellore: show running-config contains the line(s) matching interface GigabitEthernet0/0\.42 … encapsulation dot1Q 42 … ip address 192\.168\.76\.1 . 3 Sub-interface Gi0/0.43 uses dot1Q 43 and is the gateway of Engineering 25 On R-Nellore: show running-config contains the line(s) matching interface GigabitEthernet0/0\.43 … encapsulation dot1Q 43 … ip address 192\.168\.176\.1 . 4 Faculty reaches Engineering 25 On Faculty-PC: ping 192.168.176.10 must succeed.
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
Common mistakes
Forgetting no shutdown on the physical interface
Sub-interface number and dot1Q id that disagree
Trunk allowed list missing a VLAN
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:
SW-Nellore interface g0/1
switchport mode trunk
exit R-Nellore interface g0/0
no shutdown
exit
interface g0/0.42
encapsulation dot1Q 42
ip address 192.168.76.1 255.255.255.0
exit
interface g0/0.43
encapsulation dot1Q 43
ip address 192.168.176.1 255.255.255.0
exit Where this is examined
CCNA 2.0 inter-VLAN routing.
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