Basic networking concepts - Learn Tech From Zero

4.4 Your Computer on the Network (Weight: 2)

📘Linux Essentials (LPI 010-160)

1. What is a Network?

A network is a group of computers and devices connected together to share data and resources like files, printers, or internet access.

Local Area Network (LAN): A network within a building or office. Example: Multiple computers in a small office connected to a shared printer.
Wide Area Network (WAN): A network that covers a large geographic area, like connecting multiple offices in different cities.
Internet: The largest WAN, connecting millions of networks globally.

2. Network Devices

These are devices that help computers connect and communicate:

Router: Directs traffic between different networks. Example: Connects your office LAN to the internet.
Switch: Connects multiple devices in the same network (LAN) and forwards data to the correct device.
Access Point (AP): Provides wireless (Wi-Fi) connectivity to devices.
Network Interface Card (NIC): The hardware inside a computer that allows it to connect to a network.

3. IP Addresses

An IP (Internet Protocol) address is like a digital address that identifies a device on a network.

IPv4: Most common, 32-bit address, written as four numbers separated by dots (e.g., 192.168.1.10).
IPv6: Newer, 128-bit address, written in hexadecimal (e.g., 2001:0db8:85a3::8a2e:0370:7334).

Example in IT: A server in a data center might have IP 192.168.100.50, allowing other servers to connect and access its services.

4. Subnets and Masks

Networks can be divided into smaller parts called subnets.

Subnet mask: Determines which part of the IP is the network and which part is the device.
Example: IP 192.168.1.10 with subnet mask 255.255.255.0 → Network is 192.168.1.0 and devices are 1–254.

IT example: In a corporate LAN, the subnet ensures departments like HR, IT, and Sales have separate IP ranges.

5. Default Gateway

The default gateway is the router that connects your network to other networks or the internet.
Example: Your office LAN computers use the gateway 192.168.1.1 to access cloud services.

6. DNS (Domain Name System)

Converts human-friendly names (like www.example.com) into IP addresses (93.184.216.34).
IT usage: When employees type intranet.company.com, DNS resolves it to the internal server IP automatically.

7. Ports and Protocols

Protocols are rules for how data moves across a network.
Common protocols in Linux/IT:

Protocol	Port	Purpose
HTTP	80	Accessing websites
HTTPS	443	Secure web access
SSH	22	Remote server login
FTP	21	File transfer
SMTP	25	Sending emails

IT example: A Linux admin uses SSH (port 22) to securely manage a server from home.

8. Network Commands in Linux

Linux has commands to check and manage networks:

ifconfig / ip addr → Shows your IP addresses and network interfaces.
ping <IP> → Tests if another device is reachable.
traceroute <IP> → Shows the path packets take to reach a device.
netstat / ss → Shows active connections and listening ports.
nslookup <domain> or dig <domain> → Checks DNS resolution.

Example: A sysadmin might run ping 192.168.1.1 to see if the office router is working.

9. Static vs Dynamic IP

Static IP: Manually assigned; does not change. Used for servers.
Dynamic IP: Assigned automatically by a DHCP server. Common for desktops and laptops.

IT example: Web servers usually have static IPs so clients always know where to connect.

10. MAC Address

Every network interface has a MAC (Media Access Control) address, a unique hardware identifier.
Format: 00:1A:2B:3C:4D:5E
IT use: Network security can restrict access to certain MAC addresses.

11. Firewalls

A firewall controls incoming and outgoing traffic based on rules.
Linux often uses iptables or firewalld to secure servers.
Example: Only allow SSH (port 22) and block all other unused ports.

Summary: Key Points for the Exam

Network basics: LAN, WAN, Internet.
Devices: Router, switch, access point, NIC.
IP addressing: IPv4/IPv6, subnet, gateway.
DNS resolves names to IPs.
Ports and protocols for communication.
Linux network commands: ping, ifconfig/ip, traceroute, netstat, dig/nslookup.
Static vs dynamic IPs.
MAC address is unique per device.
Firewalls secure traffic.

These are the essentials for basic networking concepts in the Linux Essentials exam. Understanding them helps you work with Linux servers, desktops, and cloud services efficiently in real IT environments.