> For the complete documentation index, see [llms.txt](https://recondock.gitbook.io/recondock/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://recondock.gitbook.io/recondock/cybersecurity-playbook/connection-security/ip-addressing-basics.md).

# IP Addressing Basics

* **IPv4**: `192.168.1.1` (32-bit, decimal)
  * Private Ranges:
    * `10.0.0.0/8`
    * `172.16.0.0/12`
    * `192.168.0.0/16`
* **IPv6**: `2001:0db8:85a3::8a2e:0370:7334` (128-bit, hex)
  * Shorthand: Replace consecutive zeros with `::` once.

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### **Subnetting Essentials**

#### **IPv4 Subnet Mask Shortcuts**

| CIDR | Subnet Mask       | Hosts per Subnet |
| ---- | ----------------- | ---------------- |
| /24  | `255.255.255.0`   | 254              |
| /30  | `255.255.255.252` | 2                |

**Formula**:

* Hosts = 2(32−CIDR)−22(32−CIDR)−2
* Example: `/26 = 64 - 2 = 62 hosts`.

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### **Common Protocols & Ports**

| Protocol | Port  | Use Case                |
| -------- | ----- | ----------------------- |
| HTTP     | 80    | Unencrypted web traffic |
| HTTPS    | 443   | Encrypted web traffic   |
| SSH      | 22    | Secure remote access    |
| DNS      | 53    | Domain name resolution  |
| DHCP     | 67/68 | Dynamic IP assignment   |

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### **Network Troubleshooting Commands**

* **`ping <IP>`**: Test connectivity.
* **`tracert <IP>` (Windows) / `traceroute <IP>` (Linux)**: Map path to destination.
* **`ipconfig` (Windows) / `ifconfig` (Linux)**: View interface details.
* **`netstat -ano`**: List active connections and ports.
* **`nslookup <domain>`**: Query DNS records.

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### **Security Best Practices**

1. **Firewall Rules**:
   * Block all inbound traffic by default.
   * Allow only necessary ports (e.g., 443 for HTTPS).
2. **Use VLANs** to segment traffic (e.g., separate guest and internal networks).
3. **Disable unused ports** on switches/routers.
4. **Always use SSH** instead of Telnet.

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### **Quick Reference Tables**

#### **OSI Model Layers**

| Layer | Name        | Example         |
| ----- | ----------- | --------------- |
| 7     | Application | HTTP, FTP       |
| 4     | Transport   | TCP, UDP        |
| 3     | Network     | IP, ICMP        |
| 2     | Data Link   | MAC addresses   |
| 1     | Physical    | Cables, signals |

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### **Pro Tips**

🔹 Use **Wireshark** to analyze traffic patterns.\
🔹 Memorize private IP ranges to avoid conflicts.\
🔹 For labs: `/30` subnets = perfect for point-to-point links.

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### **Where to Learn More**

* **Cisco NetAcad**: Free networking labs.
* **TryHackMe**: Hands-on network security rooms.
* **RFC 1918**: Private IP address standards.
* **Cisco Packet Tracer**

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**Fun Fact**: The first RFC (Request for Comments) was written in 1969 to define ARPANET protocols—the precursor to the modern internet!

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