Wires Are Not Enough

Lesson 3 of 35 in Coddy's LAN Labs course.

Cabled does not mean connected. A cable carries signals, but a device can only be addressed once it has an IP address, and netlab is honest about that: pinging an unaddressed host fails with the exact reason.

netlab show ip is the addressing view of the lab: one line per interface, with its address, mask and gateway, or a dash where nothing is configured yet. netlab ping A B asks whether A can reach B and, when it cannot, tells you why in one line.

Get used to reading those reasons. Real networks fail silently; the lab never does.

Challenge

Beginner

The two hosts are cabled to sw1 but have no addresses. Show the addressing view, then try to ping pc2 from pc1.

Expected output:

NODE  IFACE  ADDRESS  MASK  GATEWAY
pc1   eth0   -        -     -
pc2   eth0   -        -     -
pc1 -> pc2: unreachable (pc1 has no IP address)

Try it yourself

Terminal

All lessons in LAN Labs

1Meet the Lab

Your First Lab CablesWires Are Not EnoughRecap - 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 Subnet Let check Do the Looking Recap - 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