📌 Overview
NetPractice is a core project from the 42 curriculum designed to teach and test your understanding of computer networking fundamentals. Instead of coding, this project uses an interactive learning platform where you configure small networks (IP addressing, routing, masks, subnets, gateways) until every machine can reach its target.
Through practical exercises, you’ll build a solid foundation in how data actually flows across networks — knowledge that underpins everything from local LAN setups to the global Internet.
- 🌐 Configure IPv4 addressing across multiple subnets
- 🛣️ Set up default gateways and routing tables
- 🎯 Learn to calculate and assign subnet masks
- 🧮 Understand binary/decimal IP conversion
- 📡 Troubleshoot and fix broken connectivity step by step
- 🔗 Visualize how packets travel across a network
- 🧭 Develop intuition for OSI vs TCP/IP model layers
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An IP address identifies a device on a network.
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Written in dotted decimal notation (e.g.,
192.168.1.10). -
Consists of:
- Network part: identifies the subnet.
- Host part: identifies the device inside that subnet.
➡️ Example: 192.168.1.10/24
/24means the first 24 bits are the network.- Network =
192.168.1.0, Host =.10
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A mask defines how many bits belong to the network.
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Example masks:
/24→ 255.255.255.0 → 254 usable hosts/30→ 255.255.255.252 → 2 usable hosts (for point-to-point links)
➡️ Subnetting lets you split a large network into smaller, efficient ones.
- A router connects multiple networks.
- Each machine can only talk directly to devices on the same subnet.
- To reach outside, it must send traffic to a gateway (usually the router).
➡️ Example:
- PC A:
10.0.1.5/24, Gateway =10.0.1.1 - Destination =
10.0.2.5/24 - PC A sends to
10.0.1.1(router), which forwards to10.0.2.5.
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Private ranges:
10.0.0.0/8172.16.0.0/12192.168.0.0/16
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Used for internal networks, not routable on the Internet.
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Public IPs are globally unique and reachable over the Internet.
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Layers of communication:
- Physical → Data Link → Network → Transport → Application
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In NetPractice you mainly focus on the Network layer (IP addresses, routes) but you’ll understand how it interacts with:
- Transport layer (TCP/UDP ports)
- Data Link layer (MAC addresses)
- Wrong subnet mask → devices think they’re in the same network when they’re not.
- No default gateway → can’t reach outside the local subnet.
- Overlapping subnets → routing confusion.
- Misconfigured routes → packets get lost.
- 🧮 Subnetting math (binary & CIDR notation)
- 🖧 Building networks from scratch
- 🛣️ Understanding routing logic (longest prefix match)
- 🧭 Debugging misconfigurations (step-by-step testing)
- Log into the NetPractice platform provided by 42.
- Complete levels in order — each introduces a new concept (IP assignment, subnetting, routing, multiple routers, etc.).
- Verify connectivity by pinging targets in the UI.
- PC1 → IP:
192.168.1.2/24 - PC2 → IP:
192.168.1.3/24✅ Both can ping each other (same subnet).
If PC2 is instead 10.0.0.2/24:
❌ No direct connection.
➡️ You must add a router with:
- Interface1:
192.168.1.1/24 - Interface2:
10.0.0.1/24Then set gateways on both PCs.
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Always check:
- IP addresses
- Subnet masks
- Default gateways
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Convert between binary & decimal to see how subnets work.
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Use
/30subnets for router-to-router links (efficient). -
Think of the network as a map: every device must know how to reach its destination.
- No coding, all configuration is manual logic.
- Must fully understand why each fix works.
- Solutions should follow best networking practices.
By finishing NetPractice, you’ll:
- Build confidence in real-world networking.
- Be able to configure LANs, routers, and troubleshoot IP issues.
- Gain a foundation that helps for future DevOps, SysAdmin, and Cloud engineering paths.