> Source: [sk27307](https://support.checkpoint.com/results/sk/sk27307)

# sk27307 - Differences between public and private IP addresses

| Property | Value |
|----------|-------|
| Solution ID | sk27307 |
| Date Created | 2004-09-30 |
| Last Modified | 2017-01-24 |
| Technical Level | General |
| Products | Other |
| Versions | Not Version-Specific |

## Symptoms

- What are the differences between public and private IP addresses?

## Solution

The Internet Assigned Numbers Authority (IANA) defined the following blocks of IP addresses for use on private networks:  

Class A networks: 10.0.0.0 to 10.255.255.255  
Class B networks: 172.16.0.0 to 172.31.255.255  
Class C networks: 192.168.0.0 to 192.168.255.255  

These IP addresses are not routable on the public Internet. As defined in RFC 1918, private IP addresses can be used by any individual or enterprise for hosts on a private network that are not directly connected to the Internet. All hosts connected to the Internet must have a publicly routable address.  

Administrators can use the Network Address Translation (NAT) features of VPN-1/FireWall-1 to connect privately addressed hosts to the Internet, using publicly routable IP addresses. Administrators may also define specific address ranges that the VPN-1/FireWall-1 Security Gateway considers private. Configure this function on the NAT page of the Global Properties screen.

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