🚧 Part 3: Networking

Caution

This section is under development. Thank you for your patience.

This section provides and introduction to Linux networking. We’ll cover some foundational theory and hands-on configuration on Ubuntu (22.04+) and RHEL 9 operating systems. Each chapter includes a Common Commands box highlighting distro-specific tools and syntax.

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Networking Fundamentals

• OSI & TCP/IP Models
• IPv4 vs. IPv6 Addressing
• MAC Addresses & ARP
• Common Protocols (ICMP, DHCP, DNS, HTTP/S)

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Network Configurations

• DHCP vs. Static Assignment
  
• Ubuntu: Netplan
  • /etc/netplan/*.yaml syntax
    
  • sudo netplan apply
• RHEL 9: NetworkManager & legacy scripts
  • nmcli CLI: nmcli connection add/modify
    
  • nmtui TUI
    
  • (Optional) /etc/sysconfig/network-scripts/ifcfg-*
• Bringing Interfaces Up/Down

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Domain Name System

• DNS & Name Resolution
  
• /etc/hosts Basics
  
• Resolver Configuration
  • Ubuntu: systemd-resolved, /etc/resolv.conf symlink
    
  • RHEL 9: direct /etc/resolv.conf
• Testing DNS
• Caching & Stub Resolvers

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Routing & IP Management

• Static Routes
• Policy-Based Routing (ip rule)
• Enabling IP Forwarding
• VRFs & Network Namespaces

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Firewalling & Network Security

• Ubuntu UFW (Uncomplicated Firewall)
  • sudo ufw enable/disable
    
  • Profile management
• RHEL 9 firewalld
  • sudo firewall-cmd --zone=public --add-port=80/tcp
    
  • Permanent vs. runtime rules
• iptables vs. nftables
  
• SELinux & Network Access

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Monitoring & Troubleshooting

• Connectivity Tests (ping, traceroute, mtr)
• Socket & Port Inspection (ss, netstat)
• Packet Capture (tcpdump, tshark)
• Interface Statistics (ethtool, iftop, nload)
• Logs & Systemd Journal

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VPNs, Encryption, & Tunnels

• SSH Tunnels & SOCKS Proxies
• OpenVPN Setup
• WireGuard Quick-Start
• IPsec & strongSwan

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Linux Virtual & Container Networking

• Bridge & VLAN Interfaces
• Docker & Podman Networks
• CNI Plugins & Kubernetes Basics
• MACVLAN, NAT & Host Networking Modes