Networks are how your devices talk to each other and the internet. Understanding the basics helps you diagnose connectivity problems and get the most out of netglance.

What it is¶

A network is a group of computers and devices connected together so they can share information. Your home network includes your router, your laptop, your phone, smart speakers, and anything else connected via WiFi or Ethernet. These devices communicate using a shared language called the Internet Protocol (IP).

Every device on your network has an IP address—a unique numerical identifier, like 192.168.1.42. This address is how devices find and talk to each other. Your network is divided into smaller groups called subnets so traffic stays organized. Your router acts as the gatekeeper, controlling what goes to the internet and what stays local.

Why it matters for your network¶

If a device can't talk to others or reach the internet, it's usually a network configuration problem. Maybe it didn't get a valid IP address. Maybe the router isn't forwarding traffic correctly. Maybe a device is on the wrong subnet. By understanding how networks work, you can:

• Diagnose why a device loses connectivity
• Understand what netglance is telling you
• Plan your network layout (how many devices, what IP ranges, etc.)
• Spot security issues like unauthorized devices or address conflicts

How it works¶

IP Addresses¶

An IP address (IPv4) looks like 192.168.1.42—four numbers separated by dots, each ranging from 0–255. Think of it like a mailing address: the router needs this to know where to send data.

Every device on your LAN (local area network) shares a common portion of the address. For example, if your router is at 192.168.1.1, all your devices might be 192.168.1.x (where x is unique per device). This shared portion is the subnet.

Subnets and CIDR Notation¶

A subnet divides a network into logical groups. The notation 192.168.1.0/24 means: - 192.168.1.0 is the network address - /24 means the first 24 bits (out of 32) identify the network; the remaining 8 bits identify individual hosts

In this /24 subnet: - 192.168.1.0 is the network address (reserved) - 192.168.1.1 through 192.168.1.254 are usable device addresses - 192.168.1.255 is the broadcast address (reserved, used to reach all devices at once)

Common home network sizes: - /24 (255 addresses): typical home network - /25 (128 addresses): small network - /16 (65,535 addresses): large network (rarely used at home)

Default Gateway¶

Your default gateway is the device (usually your router) that forwards traffic destined for outside your LAN. If your laptop wants to reach Google, it sends the packet to the gateway, which then routes it toward the internet.

Every device needs to know its gateway's IP address. Without it, devices can only talk to others on the same subnet—no internet. The gateway is typically x.x.x.1 in your subnet (e.g., 192.168.1.1).

LAN vs WAN¶

LAN (Local Area Network) = your home network. All devices here can talk directly using their private IP addresses.

WAN (Wide Area Network) = the internet. Your router connects your LAN to the WAN via your ISP (Internet Service Provider).

NAT (Network Address Translation)¶

Your router uses NAT to translate between private and public IPs: - Inside: devices use private addresses like 192.168.1.42 - Outside: the ISP assigns your router one public IP (e.g., 203.0.113.45)

When your laptop sends a request to Google, the router rewrites the "from" address to the public IP. When Google responds, the router rewrites it back to 192.168.1.42. This keeps your device addresses hidden and conserves the limited pool of public IPs.

DHCP Leases¶

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices on your network. When you connect a phone to WiFi, the router's DHCP server hands it an address like 192.168.1.105 for a fixed time period—the lease duration (typically 24–48 hours).

When the lease expires, the device either: 1. Requests renewal (same or different address) 2. Loses connectivity and requests a new address

Static assignment means an administrator (you) manually assigns a specific IP to a device, bypassing DHCP. Useful for servers, printers, and IoT devices so their address doesn't change.

Private vs Public IP¶

Private IPs (RFC 1918 ranges) are reserved for internal use: - 10.0.0.0 – 10.255.255.255 (Class A) - 172.16.0.0 – 172.31.255.255 (Class B) - 192.168.0.0 – 192.168.255.255 (Class C)

Every home network uses private IPs. They're never routable on the public internet—ISPs drop them.

Public IPs are unique worldwide and routable on the internet. Your ISP assigns one to your router's WAN port. Servers and services use public IPs so anyone can reach them.

Network Topology Diagram¶

graph LR
    Internet["🌐 Internet<br/>(WAN)"]
    Modem["📡 Modem<br/>(ISP connection)"]
    Router["🔄 Router<br/>192.168.1.1<br/>(gateway)"]

    WiFi["📶 WiFi Network<br/>192.168.1.0/24"]
    Wired["🔌 Wired<br/>192.168.1.0/24"]

    Laptop["💻 Laptop<br/>192.168.1.42"]
    Phone["📱 Phone<br/>192.168.1.105"]
    TV["📺 Smart TV<br/>192.168.1.50"]
    IoT["🏠 IoT Device<br/>192.168.1.200"]
    Printer["🖨️ Printer<br/>192.168.1.25"]

    Internet -->|WAN| Modem
    Modem --> Router
    Router --> WiFi
    Router --> Wired

    WiFi -->|DHCP| Laptop
    WiFi -->|DHCP| Phone
    WiFi -->|Static| TV
    WiFi -->|Static| IoT

    Wired -->|Static| Printer

    style Internet fill:#e1f5ff
    style Modem fill:#fff3e0
    style Router fill:#f3e5f5
    style WiFi fill:#e8f5e9
    style Wired fill:#fce4ec

In this diagram: - The router is the hub connecting LAN devices to the modem (and internet) - All LAN devices get private IPs in the 192.168.1.0/24 subnet - Some devices use DHCP (auto-assigned), others have static IPs - The router's DHCP server issues leases for devices like the laptop and phone

What netglance checks¶

netglance discover — Scans your subnet to find all active devices and their IP addresses. Shows you what's connected right now.

netglance ping — Tests connectivity to a device (like your gateway or an internet host). Tells you if a device is reachable and how fast the response is.

netglance route — Traces the path packets take from your device to a destination (like 8.8.8.8). Shows each hop (router, ISP gateway, etc.) along the way. Useful for diagnosing slow or broken paths.

netglance dns — Checks DNS resolution on your network. Ensures your gateway (or configured DNS server) is translating domain names to IPs correctly.

Key terms¶

Further reading¶

• RFC 1918 — Private Internet Addresses
• CIDR Notation Explained
• How DHCP Works
• NAT and Port Forwarding
• traceroute and Understanding Route Paths