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Secure management 57 — SSH only from the admin LAN
Security Intermediate 2 devices 5 checked tasks 100 points Plan lab
Edge-Nellore still accepts Telnet from anywhere. Name it, give it a domain and RSA key, add local user noc, allow only SSH version 2, and let only the admin LAN 10.76.1.0/24 through (access-class 66). 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
Edge-Nellore still accepts Telnet from anywhere. Name it, give it a domain and RSA key, add local user noc, allow only SSH version 2, and let only the admin LAN 10.76.1.0/24 through (access-class 66).
Your role: a security engineer. Level: Intermediate Done when: all 5 goals show as passed (100 points).
Network status
Devices: 1 router, 1 PC, cabled as drawn. No Layer 1 or Layer 2 faults: every link is connected and up. Router starts with addresses (G0/0 10.76.1.1/24). Admin-PC is a host with 10.76.1.10/24, gateway 10.76.1.1. 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
The router is named Edge-Nellore (10 pts) Domain nellore.lab and local user noc exist (20 pts) SSH version 2 is on (15 pts) The VTY lines accept SSH only, with local login (30 pts) Only the admin LAN may connect (access-class 66) (25 pts) The activity, in order
The router is named Edge-Nellore 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 Domain nellore.lab and local user noc exist 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 SSH version 2 is on 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 The VTY lines accept SSH only, with local login 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 Only the admin LAN may connect (access-class 66) Why: The login prompt is the most attacked door on the device; an ACL narrows who may even knock. Verify with: show running-config | section line vty 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: Generating the RSA key while the router is still called Router Common mistake: transport input ssh without login local — no way to log in Common mistake: Applying the ACL with ip access-group instead of access-class Why this matters
Telnet sends the password in clear text. SSH encrypts the session, but only once the router has a name, a domain and an RSA key; an access-class then limits who may even try.
What you will be able to do
Prepare a router for SSH (hostname, domain, key, user)
Restrict VTY lines to SSH and an ACL
Verify with show ip ssh
The network
ISR 2911, PC — 2 devices in all, already cabled.
Fa0 Gi0/0 10.76.1.1/24 Router Admin-PC 10.76.1.10/24 · gw 10.76.1.1 Drawn from this lab: devices, cables, ports and the addresses already set. Device Model Address already set
Router ISR 2911 configure it Admin-PC PC 10.76.1.10 / 255.255.255.0 gw 10.76.1.1
Cabling
Admin-PC Fa0 ↔ Router Gi0/0
What is configured at the start
These are already configured when the lab opens — including, where this is a troubleshooting lab, the fault itself:
Router interface g0/0
ip address 10.76.1.1 255.255.255.0
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 The router is named Edge-Nellore 10 On Router: show running-config contains the line(s) matching hostname Edge-Nellore. 2 Domain nellore.lab and local user noc exist 20 On Router: show running-config contains the line(s) matching ip domain-name nellore\.lab. and On Router: show running-config contains the line(s) matching username noc . 3 SSH version 2 is on 15 On Router: show running-config contains the line(s) matching ip ssh version 2. 4 The VTY lines accept SSH only, with local login 30 On Router: show running-config contains the line(s) matching transport input ssh. and On Router: show running-config contains the line(s) matching line vty … login local. 5 Only the admin LAN may connect (access-class 66) 25 Checked automatically against the device’s live state (vtyAcl).
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
Generating the RSA key while the router is still called Router
transport input ssh without login local — no way to log in
Applying the ACL with ip access-group instead of access-class
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:
Router hostname Edge-Nellore
ip domain-name nellore.lab
username noc secret Adm1n#66
crypto key generate rsa modulus 2048
ip ssh version 2
access-list 66 permit 10.76.1.0 0.0.0.255
line vty 0 4
login local
transport input ssh
access-class 66 in
exit Where this is examined
CCNA 5.3 device access control; Security+ 4.5; CCNP ENCOR infrastructure security.
This lab practises these topics in the zNetLaB certification courses:
Related labs
Where to start
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