Fix the Address Clash

Lesson 33 of 35 in Coddy's LAN Labs course.

Start with the ERROR: two hosts on the second floor share 192.168.20.11. Until that is fixed, nothing on that floor is trustworthy, because frames for that address may land on either machine.

When two devices clash, move the one that arrived later, so the machine users already know keeps its address. Then confirm the pair can talk: a same-subnet ping through the switch should come back with ttl=64.

Challenge

Easy

Give h5 the free address 192.168.20.13/24, then ping h3 from h5.

Expected output:

h5 eth0: 192.168.20.13/24 (mask 255.255.255.0, network 192.168.20.0/24)
h5 -> h3: reply from 192.168.20.11 (ttl=64)

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 DamageFix the Address ClashMasks 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