IPv4 Address and Net Mask
When representing hosts by an IP address with a netmask, the IP address can represent one or more hosts. For example, a firewall address can be:
• A single host such as a single computer with the address 192.45.46.45
• A range of hosts such as all of the hosts on the subnet 192.45.46.1 to 192.45.46.255
• All hosts, represented by 0.0.0.0 which matches any IP address
The netmask corresponds to the subnet class of the address being added, and can be represented in either dotted decimal or CIDR format. The FortiGate unit automatically converts CIDR formatted netmasks to dotted decimal format. Example formats:
• Netmask for a class A subnet of 16,777,214 usable addresses: 255.0.0.0, or /8
• Netmask for a class B subnet of 65,534 usable addresses: 255.255.0.0, or /16
• Netmask for a class C subnet of 254 usable addresses: 255.255.255.0, or /24
• Netmask for subnetted class C of 126 usable addresses: 255.255.255.128, or /25
• Netmask for subnetted class C of 62 usable addresses: 255.255.255.128, or /26
• Netmask for subnetted class C of 30 usable addresses: 255.255.255.128, or /27
• Netmask for subnetted class C of 14 usable addresses: 255.255.255.128, or /28
• Netmask for subnetted class C of 6 usable addresses: 255.255.255.128, or /29
• Netmask for subnetted class C of 2 usable addresses: 255.255.255.128, or /30
• Netmask for a single computer: 255.255.255.255, or /32
• Netmask used with 0.0.0.0 to include all IP addresses: 0.0.0.0, or /0
So for a single host or subnet the valid format of IP address and netmask could be either:
x.x.x.x/x.x.x.x, such as 192.168.1.0/255.255.255.0
or
x.x.x.x/x, such as 192.168.1.0/24
It is also possible to describe a range of IP addresses with a subnet. This would be a continuous set of IP addresses within a subnet. It does not have to include the whole subnet. The formats would be (the * being used as a wildcard character):
x.x.x.x-x.x.x.x, such as 192.168.110.100-192.168.110.120
x.x.x.[x-x], such as 192.168.110.[100-120]
x.x.x.*, such as 192.168.110.*