Module 6: Networking

Lesson 1: Network Configuration

1.1 Configuring Network Interfaces

1.1.1 Checking Network Interfaces

ifconfig or ip addr: Display information about network interfaces.

ifconfig

1.1.2 Configuring Network Interfaces

ifconfig or ip addr: Manually configure network interfaces.

sudo ifconfig eth0 192.168.1.2 netmask 255.255.255.0

ip Command:

sudo ip addr add 192.168.1.2/24 dev eth0

1.1.3 Network Configuration Files

/etc/network/interfaces (Debian/Ubuntu):

auto eth0

iface eth0 inet static

    address 192.168.1.2

    netmask 255.255.255.0

/etc/sysconfig/network-scripts/ifcfg-eth0 (Red Hat/CentOS):

DEVICE=eth0

BOOTPROTO=static

IPADDR=192.168.1.2

NETMASK=255.255.255.0

1.2 Troubleshooting Network Issues

ping: Check network connectivity.

ping google.com

traceroute or tracepath: Trace the route to a destination. 

traceroute google.com

netstat or ss: Display network statistics and connections. 

netstat -tuln

Lesson 2: Firewall Configuration

2.1 Introduction to iptables or firewalld

2.1.1 iptables

Viewing Rules: 

sudo iptables -L

Allowing Connections: 

sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT

Blocking Connections:

sudo iptables -A INPUT -p tcp --dport 80 -j DROP

2.1.2 firewalld

Checking Zones:

sudo firewall-cmd --get-active-zones

Opening Ports:

sudo firewall-cmd --zone=public --add-port=80/tcp --permanent

Reloading Firewall:

sudo firewall-cmd --reload

In Module 6, we explored the intricacies of networking in Linux system administration. We delved into network configuration, learning how to check and manually configure network interfaces using tools like ifconfig, ip, and configuration files. Troubleshooting network issues was addressed through commands like ping, traceroute, and netstat. Additionally, we introduced firewall configuration with a focus on iptables and firewalld, covering the basics of allowing and blocking connections. As we advance in our Linux journey, mastering networking concepts is essential for maintaining connectivity, resolving issues, and securing our systems against potential threats.