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Guest isolation 51 — a named ACL for the guest LAN
Security Advanced 4 devices 5 checked tasks 100 points Plan lab
Scenario — Gwalior gives visitors Wi-Fi on their own subnet (10.70.3.0/24). Guests may reach the internet server (10.70.9.10) but must never reach the staff LAN (10.70.1.0/24). Write the named extended ACL GUEST-IN, deny IP from the guest subnet to the staff subnet, permit everything else, and apply it inbound on the guest-facing port Gi0/1. Staff must still reach the internet server. 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
Gwalior gives visitors Wi-Fi on their own subnet (10.70.3.0/24). Guests may reach the internet server (10.70.9.10) but must never reach the staff LAN (10.70.1.0/24). Write the named extended ACL GUEST-IN, deny IP from the guest subnet to the staff subnet, permit everything else, and apply it inbound on the guest-facing port Gi0/1. Staff must still reach the internet server.
Your role: a security engineer. Level: Advanced Done when: all 5 goals show as passed (100 points).
Network status
Devices: 1 router, 3 PCs, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. Edge-Gwalior starts with addresses (G0/0 10.70.1.1/24, G0/1 10.70.3.1/24, G0/2 10.70.9.1/24). Staff-PC is a host with 10.70.1.10/24, gateway 10.70.1.1. Guest-PC is a host with 10.70.3.10/24, gateway 10.70.3.1. Internet-Server is a host with 10.70.9.10/24, gateway 10.70.9.1. 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
GUEST-IN denies IP from 10.70.3.0/24 to 10.70.1.0/24 and permits the rest (35 pts) GUEST-IN is applied inbound on the guest port Gi0/1 (20 pts) A guest cannot reach the staff LAN (20 pts) A guest still reaches the internet server (15 pts) Staff still reach the internet server (10 pts) The activity, in order
GUEST-IN denies IP from 10.70.3.0/24 to 10.70.1.0/24 and permits the rest 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 GUEST-IN is applied inbound on the guest port Gi0/1 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 A guest cannot reach the staff LAN Why: Blocking traffic is half of security. You prove a block by showing the same ping that worked before now fails. Verify with: ping 10.70.1.10 A guest still reaches the internet server Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.70.9.10 Staff still reach the internet server Why: A ping needs a route in BOTH directions. This is the end-to-end proof that everything before it worked. Verify with: ping 10.70.9.10 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: Applying outbound on the staff port and blocking replies Common mistake: Wrong wildcard — a /24 written as 0.0.0.0 Common mistake: Forgetting the final permit Why this matters
Visitors need the internet but not your file servers. A named ACL on the guest port, inbound, drops anything aimed at the staff subnet and lets the rest through — and a name is easier to read and edit than a number.
What you will be able to do
Write a named extended ACL
Match subnets with wildcard masks
Place the ACL on the guest-facing port
The network
ISR 2911, PC — 4 devices in all, already cabled.
Fa0 Gi0/0 10.70.1.1/24 Fa0 Gi0/1 10.70.3.1/24 Fa0 Gi0/2 10.70.9.1/24 Edge-Gwalior Staff-PC 10.70.1.10/24 · gw 10.70.1.1 Guest-PC 10.70.3.10/24 · gw 10.70.3.1 Internet-Server 10.70.9.10/24 · gw 10.70.9.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
Edge-Gwalior ISR 2911 configure it Staff-PC PC 10.70.1.10 / 255.255.255.0 gw 10.70.1.1 Guest-PC PC 10.70.3.10 / 255.255.255.0 gw 10.70.3.1 Internet-Server PC 10.70.9.10 / 255.255.255.0 gw 10.70.9.1
Cabling
Staff-PC Fa0 ↔ Edge-Gwalior Gi0/0 Guest-PC Fa0 ↔ Edge-Gwalior Gi0/1 Internet-Server Fa0 ↔ Edge-Gwalior Gi0/2
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
Edge-Gwalior interface g0/0
ip address 10.70.1.1 255.255.255.0
no shutdown
exit
interface g0/1
ip address 10.70.3.1 255.255.255.0
no shutdown
exit
interface g0/2
ip address 10.70.9.1 255.255.255.0
no shutdown
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 GUEST-IN denies IP from 10.70.3.0/24 to 10.70.1.0/24 and permits the rest 35 On Edge-Gwalior: show running-config contains the line(s) matching ip access-list extended GUEST-IN[\s\S]*deny ip 10\.70\.3\.0 0\.0\.0\.255 10\.70\.1\.0 0\.0\.0\.255[\s\S]*permit ip any any. 2 GUEST-IN is applied inbound on the guest port Gi0/1 20 On Edge-Gwalior: show running-config contains the line(s) matching interface GigabitEthernet0/1 … ip access-group GUEST-IN in. 3 A guest cannot reach the staff LAN 20 On Guest-PC: ping 10.70.1.10 must fail — the policy blocks it. 4 A guest still reaches the internet server 15 On Guest-PC: ping 10.70.9.10 must succeed. 5 Staff still reach the internet server 10 On Staff-PC: ping 10.70.9.10 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
Applying outbound on the staff port and blocking replies
Wrong wildcard — a /24 written as 0.0.0.0
Forgetting the final permit
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:
Edge-Gwalior ip access-list extended GUEST-IN
deny ip 10.70.3.0 0.0.0.255 10.70.1.0 0.0.0.255
permit ip any any
exit
interface g0/1
ip access-group GUEST-IN in
exit Where this is examined
CCNA 5.6 ACLs; Security+ 3.2 network segmentation.
This lab practises these topics in the zNetLaB certification courses:
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