Network Configuration

Basic Networking Concepts

Network Fundamentals

IP Addressing (IPv4/IPv6)
Subnet masks and CIDR notation
Default gateways
DNS resolution

Network Protocols

TCP/IP protocol suite
Common ports and services
Network layers (OSI model)
Routing basics

Network Interface Configuration

Interface Management

ip addr show           # Show interface addresses
ip link set eth0 up    # Enable interface
ip link set eth0 down  # Disable interface
ifconfig eth0          # Show interface config (legacy)

Static IP Configuration

# Edit network configuration
vim /etc/network/interfaces  # Debian/Ubuntu
vim /etc/sysconfig/network-scripts/ifcfg-eth0  # RHEL/CentOS

# Example configuration
auto eth0
iface eth0 inet static
    address 192.168.1.100
    netmask 255.255.255.0
    gateway 192.168.1.1
    dns-nameservers 8.8.8.8

DHCP Configuration

# Enable DHCP
auto eth0
iface eth0 inet dhcp

# DHCP client commands
dhclient eth0          # Request IP from DHCP
dhclient -r eth0       # Release DHCP lease

Network Testing and Troubleshooting

Basic Network Tools

ping host             # Test connectivity
traceroute host       # Trace packet route
dig domain            # DNS lookup
nslookup domain       # DNS query

Advanced Network Tools

netstat -tuln         # Show listening ports
ss -tuln              # Socket statistics
tcpdump -i eth0       # Capture network traffic
wireshark             # GUI packet analyzer

Firewall Management

UFW (Uncomplicated Firewall)

ufw enable            # Enable firewall
ufw allow 22          # Allow SSH
ufw deny 80           # Block HTTP
ufw status            # Show rules

Firewalld

firewall-cmd --state  # Check firewall status
firewall-cmd --list-all  # List all rules
firewall-cmd --add-service=http  # Allow HTTP
firewall-cmd --remove-service=http  # Remove HTTP

IPTables

iptables -L           # List rules
iptables -A INPUT -p tcp --dport 22 -j ACCEPT  # Allow SSH
iptables -A INPUT -p tcp --dport 80 -j DROP    # Block HTTP
iptables-save         # Save rules

Network Security

SSH Configuration

vim /etc/ssh/sshd_config  # Configure SSH server
ssh-keygen            # Generate SSH keys
ssh-copy-id user@host # Copy SSH key to server

Security Best Practices

Use strong authentication
Implement access controls
Regular security updates
Monitor network traffic

Hands-on Practice

Exercise 1: Network Configuration

Configure static IP:

sudo ip addr add 192.168.1.100/24 dev eth0
sudo ip route add default via 192.168.1.1

Test connectivity
Configure DNS resolution

Exercise 2: Firewall Setup

Enable firewall
Configure basic rules
Test access control

Network Monitoring

Monitoring Tools

iptraf-ng             # Interactive network monitor
bandwidthd            # Bandwidth monitoring
ntop                  # Network traffic monitor
nagios                # Network monitoring system

Performance Analysis

iperf3                # Network performance test
mtr host              # Network diagnostic tool
netperf               # Network performance benchmark

Additional Resources

Next Steps

Learn advanced networking concepts
Master firewall configuration
Study network security
Explore network automation