What is the difference between a NAT firewall and a normal firewall?

A NAT (Network Address Translation) firewall and a normal firewall serve different but sometimes overlapping purposes in network security.

1. Normal Firewall

A normal firewall is a security device or software that monitors and controls incoming and outgoing network traffic based on predefined security rules. It acts as a barrier between trusted internal networks and untrusted external networks (like the internet).

• Primary Function: Filters traffic based on IP addresses, ports, protocols, or applications.
• Types: Packet-filtering firewalls, stateful inspection firewalls, proxy firewalls, and next-generation firewalls (NGFW).
• Example: A company uses a firewall to block all incoming traffic on port 22 (SSH) except from a specific IP range to prevent unauthorized access.

2. NAT Firewall

A NAT firewall combines Network Address Translation (NAT) with basic firewall capabilities. NAT hides internal private IP addresses by translating them into a single public IP address when accessing the internet. The firewall component enforces security rules on the translated traffic.

• Primary Function:
  • NAT: Allows multiple devices on a private network to share one public IP address.
  • Firewall: Blocks unsolicited incoming traffic by default (since external requests don’t know private IPs).
• Example: A home router uses NAT to let multiple devices (phones, laptops) share one public IP. The NAT firewall blocks incoming requests unless they are responses to outgoing connections.

Key Differences

Feature	Normal Firewall	NAT Firewall
Main Purpose	Traffic filtering based on rules	Hides internal IPs (NAT) + basic traffic filtering
Incoming Traffic	Can be allowed/blocked based on rules	Usually blocked by default (unless port forwarding is set)
Outgoing Traffic	Monitored and filtered	Translates private IPs to a public IP
Use Case	Enterprise security, application-level filtering	Home networks, basic internet sharing

Cloud Example (Tencent Cloud)

• Normal Firewall: Tencent Cloud Security Group (stateful firewall for cloud servers) or Network ACL (layer 3/4 filtering).
• NAT Firewall: Tencent Cloud NAT Gateway provides NAT functionality while inherently blocking unsolicited inbound traffic. For advanced security, combine it with Security Groups.

If you need both NAT and advanced firewall features, Tencent Cloud’s NAT Gateway + Security Group setup ensures secure internet access while hiding internal IPs.