Public vs Private IP Address — What’s the Difference?

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In networking, public and private IPs serve different purposes — and understanding them is key to managing secure and efficient systems.

Private IP (Local/Internal)

  • Used by devices inside your home or office network.
  • Assigned automatically by your router (DHCP).
  • Can’t be accessed directly from the internet.
  • Common ranges:
    – `10.0.0.0 – 10.255.255.255` (Class A)
    – `172.16.0.0 – 172.31.255.255` (Class B)
    – `192.168.0.0 – 192.168.255.255` (Class C)

Commands to Check Private IP (Linux/Windows)

  • Linux (Terminal): 
    ip a  Shows all interfaces 
ifconfig  Legacy command (may require install) 
hostname -I  Quick private IP display
  • Windows (CMD): 
    ipconfig  Displays network details

Public IP (External)

  • Assigned by your ISP.
  • Used for internet communication.
  • Visible to websites and external services.

Commands to Check Public IP (Linux/Windows)

  • Linux (Terminal): 
    curl ifconfig.me 
wget -qO- icanhazip.com 
dig +short myip.opendns.com @resolver1.opendns.com
  • Windows (CMD/PowerShell): 
    nslookup myip.opendns.com resolver1.opendns.com 

    (Invoke-WebRequest ifconfig.me/ip).Content.Trim()

How NAT (Network Address Translation) Works

  • Maps multiple private IPs to a single public IP.
  • Enables internal devices to access the internet securely.

View NAT Table (Linux)

sudo iptables -t nat -L -n -v

Enable IP Forwarding (Linux)

echo 1 > /proc/sys/net/ipv4/ip_forward

You Should Know:

  • Avoid exposing private IPs in public logs.
  • Use a VPN to mask your public IP.
  • Firewall rules should restrict unnecessary inbound traffic.
  • SSH tunneling can securely route traffic via private networks.

SSH Tunnel Example

ssh -L 8080:localhost:80 user@remote-server

What Undercode Say

Understanding IP addressing is fundamental for cybersecurity. Misconfigurations can lead to breaches, so always:
– Monitor network traffic (tcpdump, Wireshark).
– Use `nmap` to scan open ports (nmap -sV <IP>).
– Implement strong firewall rules (ufw, iptables).

Expected Output:

A secure, well-configured network with clear separation between public and private IP spaces.

Prediction:

As IPv4 exhaustion continues, IPv6 adoption will rise, requiring updated security practices for dual-stack networks.

References:

Reported By: Chiraggoswami23 Cybersecurity – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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