Now things get serious. You will see two or three routers connected in a chain.
Routing table fundamentals: A router does not have a default gateway. Instead, it has a routing table that says:
Example: Router R1 connects to R2 via 10.0.0.0/30. R2 has a LAN 192.168.1.0/24.
For R1 to reach 192.168.1.4, R1 needs a route:
Destination: 192.168.1.0/24 via Gateway: 10.0.0.2
Rule in NetPractice: All routers in the path must have correct entries, both forward and return. netpractice 42 tutorial
Example:
Left host: 192.168.1.10/24 gateway 192.168.1.1
Right host: 192.168.2.10/24 gateway 192.168.2.1
Two devices can communicate directly only if they share a network (same subnet) OR are connected via a router that knows the way.
That’s it. Every puzzle reduces to this rule. Now things get serious
| Symptom | Likely Cause | Fix |
| :--- | :--- | :--- |
| "Destination unreachable" | No route back | Check return path routing table |
| No ping between same switch | Different subnets | Change IP or mask to match |
| Can't reach internet | Missing default gateway | Add 0.0.0.0/0 route on edge router |
| Router config fails | IP overlaps another network | Recalculate subnet boundaries |
| IP rejected by interface | Network ID or broadcast used | Use a host address in range |
Lena toggled her headphones and watched the welcome screen fade into the soft blue of NetPractice 42. The tutorial’s voice, warm and steady, greeted her like an old teacher.
“Welcome to NetPractice 42. We'll guide you through the basics.” A floating cursor blinked on a schematic of a small network: three nodes—Client, Firewall, Server—connected by tidy lines. Example: Router R1 connects to R2 via 10
Between network ID (+1) and broadcast (-1): 10.0.0.33 to 10.0.0.46
Why this matters in NetPractice: If you assign a host IP that equals the network ID or broadcast, the exercise will fail.
Lena clicked the Client node. A pop-up explained its role: request origin, limited resources, and a habit of expecting instant responses. She dragged a packet icon from the Client toward the Server. The packet pulsed with each hop.
The tutorial nudged her to inspect the Firewall. “Firewalls are selective storytellers,” it said. Lena adjusted a rule slider labeled “Strictness.” The packet slowed when rules tightened, then rebounded when she allowed port 443. She smiled—security wasn’t a brick wall but a conversation.