Netpractice 42 Tutorial
| Prefix | Mask | Usable IPs per subnet |
|--------|------|------------------------|
| /24 | 255.255.255.0 | 254 |
| /30 | 255.255.255.252 | 2 (perfect for two routers) |
| /16 | 255.255.0.0 | 65534 |
| /8 | 255.0.0.0 | 16 million+ |
Note: You don’t need to memorize CIDR calculations for most levels—just ensure IPs are within the network range defined by the mask.
The interface shows: *"ping from X to Y". Trace the physical path:
In later levels, you will use a "Default Gateway." Instead of listing every specific network in the Routing Table, you can say:
This means: "If you don't know where to send the packet, send it here." netpractice 42 tutorial
The mask determines which part of the IP is the network and which is the host.
Scenario: Non-directly connected networks. Routers need static routes.
Rule: A router must know where to send packets for a destination network (next-hop IP).
Example:
R1 wants to reach 192.168.2.0/24 via R2:
⇒ Add route on R1: 192.168.2.0/24 via 10.0.0.2 | Prefix | Mask | Usable IPs per
Routing table syntax in NetPractice:
Destination network → Next hop IP
💡 Debug tip: If ping fails from Client to Server, check every router’s routing table step-by-step.
Scenario: Private LAN → Router → Internet.
Final router towards internet needs a default route:
0.0.0.0/0 → next-hop (ISP gateway) This means: "If you don't know where to
All other routers propagate reachability.
NetPractice will not give you a calculator. You need to do binary math in your head or on paper. Here is the 5-minute crash course.
An IPv4 address is 32 bits divided into 4 bytes (octets), e.g., 192.168.1.1.
In binary: 11000000.10101000.00000001.00000001
