Both Sides Need a Way Back

Lesson 16 of 35 in Coddy's LAN Labs course.

The reply is a packet too, and it faces the same question in reverse: pc3 sees a request from 192.168.1.10, a foreign address, and needs its own gateway to answer. Give pc3 the router's 10.0.0.1 and the conversation closes.

Notice the TTL: 63, not 64. The router decreased it by one on the way, and netlab adds via r1 so you can see who forwarded. netlab trace A B lists the hops explicitly, the way traceroute does on a real network.

Challenge

Easy

Set pc3's gateway to 10.0.0.1, ping pc3 from pc1, then trace the path from pc1 to pc3.

Expected output:

pc3: gateway 10.0.0.1
pc1 -> pc3: reply from 10.0.0.20 (ttl=63, via r1)
trace pc1 -> pc3
1  192.168.1.1  r1
2  10.0.0.20  pc3

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 GatewayBoth Sides Need a Way BackRouting 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