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Day 4: Network Configuration and Management ​

Objectives ​

  • Understand basic networking concepts and configurations.
  • Learn to configure network interfaces.
  • Get familiar with basic network troubleshooting tools.

1. Basic Networking Concepts ​

IP Addressing

  1. IP Address

    • Unique identifier assigned to each device on a network.
    • IPv4: Consists of four octets (e.g., 192.168.1.1).
    • IPv6: Consists of eight groups of hexadecimal digits (e.g., 2001:0db8:85a3:0000:0000:8a2e:0370:7334).

  2. Subnet Mask

    • Determines the network and host portions of an IP address.
    • Common subnet mask for home networks: 255.255.255.0.

  3. Gateway

    • Device that routes traffic from a local network to other networks or the internet.

  4. DNS (Domain Name System)

    • Translates domain names (e.g., www.example.com) into IP addresses.

Network Interfaces

  1. Ethernet Interface

    • Wired network connection, typically named eth0, eth1, etc.

  2. Wireless Interface

    • Wireless network connection, typically named wlan0, wlan1, etc.

Configuring Network Interfaces

  1. Checking Network Interfaces

    • View all network interfaces:
      bash
      $ ip link show

  2. Assigning an IP Address

    • Assign an IP address to an interface:
      bash
      $ sudo ip addr add 192.168.1.100/24 dev eth0

  3. Bringing an Interface Up or Down

    • Bring up an interface:
      bash
      $ sudo ip link set eth0 up
    • Bring down an interface:
      bash
      $ sudo ip link set eth0 down

  4. Viewing IP Address Configuration

    • Display IP addresses assigned to all interfaces:
      bash
      $ ip addr show

Network Configuration Files

  1. /etc/network/interfaces (Debian-based systems)

    • Example configuration for a static IP:
      plaintext
      auto eth0
iface eth0 inet static
  address 192.168.1.100
  netmask 255.255.255.0
  gateway 192.168.1.1

  2. /etc/netplan/ (Ubuntu 18.04+)

    • Example configuration for a static IP:

      yaml
      network:
  version: 2
  ethernets:
    eth0:
      dhcp4: no
      addresses:
        - 192.168.1.100/24
      gateway4: 192.168.1.1
      nameservers:
        addresses: [8.8.8.8, 8.8.4.4]

    • Apply the configuration:

      bash
      $ sudo netplan apply

2. Network Troubleshooting Tools ​

ping Command

  • Test connectivity to another network device:
    bash
    $ ping www.google.com
  • Stop the ping command with Ctrl + C.

ifconfig Command

  • Display or configure network interfaces (deprecated in favor of ip command):
    bash
    $ ifconfig

traceroute Command

  • Display the route packets take to a network host:
    bash
    $ traceroute www.google.com

netstat Command

  • Display network connections, routing tables, interface statistics:

    bash
    $ netstat -tuln
    • -tuln: Show listening TCP and UDP ports.

nslookup Command

  • Query DNS to obtain domain name or IP address mapping:
    bash
    $ nslookup www.google.com

curl Command

  • Transfer data to or from a server, useful for testing web services:
    bash
    $ curl http://www.example.com

Practice Exercises

Exercise 1: Basic Network Configuration

  1. Check your current IP address configuration:

    bash
    $ ip addr show

  2. Assign a static IP address to eth0:

    bash
    $ sudo ip addr add 192.168.1.200/24 dev eth0

  3. Bring the eth0 interface up:

    bash
    $ sudo ip link set eth0 up

  4. Verify the new IP address:

    bash
    $ ip addr show eth0

Exercise 2: Network Troubleshooting

  1. Test connectivity to Google's DNS server:

    bash
    $ ping 8.8.8.8

  2. Use traceroute to trace the route to www.google.com:

    bash
    $ traceroute www.google.com

  3. Display network connections using netstat:

    bash
    $ netstat -tuln

  4. Perform a DNS lookup for www.google.com:

    bash
    $ nslookup www.google.com

By the end of Day 4, users will have a solid understanding of basic network configuration and management, as well as troubleshooting network issues. These skills are essential for ensuring network connectivity and diagnosing problems in a Linux environment.