Let check Do the Looking

Lesson 12 of 35 in Coddy's LAN Labs course.

Pinging every pair of machines is slow. netlab check reads the whole lab and lists the mistakes it can prove from the configuration alone: a host with no address, a device with no cable, a host without a gateway, an address used twice, a gateway outside the host's own subnet.

Each line starts with WARN (works locally but limited) or ERROR (broken). The last line counts the problems. A clean lab prints a single line: Lab check: no problems found.

Run it early and often; it is the fastest way to see what a lab is missing.

Challenge

Beginner

Four hosts were set up in a hurry. Run the lab check and read what it finds.

Expected output:

WARN  pc3: no IP address
WARN  pc4: not connected to anything
WARN  pc4: no gateway (cannot reach other subnets)
Lab check: 3 problem(s) found

Try it yourself

Terminal

All lessons in LAN Labs

1Meet the Lab

Your First Lab Cables Wires Are Not Enough Recap - Build a Lab

4Routers and Gateways

Two Networks The Default Gateway Both Sides Need a Way Back Routing Tables Recap - Connect the Floors

7Growing the Office

The Plan Sales Comes Online Engineering Joins Gateways Everywhere Recap - The Printer

2Addresses on the LAN

Giving a Host an Address The First Ping What ARP Learned The Switch Learns Too Recap - First Conversation

5Troubleshooting I

The Unplugged Host The Missing Gateway The Typo in the Mask Recap - Two Faults

8Capstone - Fix the Branch

Survey the Damage Fix the Address Clash Masks and Gateways Recap - Prove It Works

3Masks Matter

Wrong Mask, No Reply Same Switch, Other SubnetLet check Do the LookingRecap - Diagnose the Pair

6Troubleshooting II

Two Devices, One Address The Network Address Trap Gateway on the Wrong Subnet Recap - The Silent Router

Practice on your own: Terminal playground