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NAT

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NAT

Created: 2025-11-25 Tags: networking nat ip-addressing security

Description

NAT (Network Address Translation) translates private IP addresses to public IP addresses, enabling multiple devices to share a single public IP and providing a basic security layer.

Types of NAT

Static NAT

  • One-to-one mapping
  • Private IP ↔ Public IP
  • Used for servers requiring consistent public IP

Dynamic NAT

  • Pool of public IPs
  • First-come-first-served assignment
  • More public IPs than typically needed

PAT (Port Address Translation)

  • Also called NAT Overload or NAPT
  • Many-to-one with port tracking
  • Most common type (home/office routers)
  • Single public IP for multiple devices

How PAT Works

Internal Device          NAT Router         Internet Server
192.168.1.10:50000  →   203.0.113.1:50000  →  93.184.216.34:80
192.168.1.11:50001  →   203.0.113.1:50001  →  93.184.216.34:80
192.168.1.12:50002  →   203.0.113.1:50002  →  93.184.216.34:80

Security Implications

Benefits

  • Hides internal network structure
  • Reduces public IP requirements
  • Provides basic firewall functionality
  • Makes unsolicited inbound difficult

Limitations

  • Not a firewall: Don’t rely on NAT for security
  • Stateful tracking needed: Connection table required
  • Port forwarding risks: Exposing internal services
  • Complexity: Troubleshooting more difficult

Considerations

  • Breaks end-to-end connectivity principle
  • Can interfere with some protocols (SIP, FTP, IPSec)
  • NAT traversal techniques needed for P2P
  • Logging important for security tracking

Back to: 00-MOC-Cybersecurity-Roadmap

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