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The Subnet Calculator makes it easier to specify IP addresses and masks for routing.

## IPv4 Features

The Subnet Calculator converts prefix lengths into corresponding dotted quad net masks. The prefix length can be entered with the IP Address explicitly (209.68.51.199/24), or if omitted, the subnet calculator will try to determine the prefix length based on the address class. The prefix length can be adjusted by clicking on the up/down arrows next to the Prefix Length field.

The Subnet Calculator shows the traditional (classful) IP address category or pattern along the bottom of the window below the Results box.

The Subnet box allows you to examine how an IP address is split between a Routing Prefix or network number, a Subnet number (if any), and a Host Interface number (or Group ID for multicast addresses). The length in bits and value of each portion can be adjusted separately.

The Subnet Calcuator will list the subnets (if any) in the Results box along with the host address range and other information. The host address range shown includes the first and last address of the range which are normally reserved for IPv4 subnet broadcasts and thus are not assigned to individual interfaces. The "Reverse DNS" string is used for address-to-name lookups or "Pointer" (PTR) queries to a name server.

The Subnet Calculator determines the CIDR alignment based on the address class and right most 1-bit in the network prefix if an address ends in "/" with no length specified. Entering "146.111.96/" for example will show the Routing Prefix as 146.111.96.0/19.

The Subnet Calculator will accept a decimal IP address as input and convert to a dotted quad. Entering "3232235521" will display IP address 192.168.0.1 for example. This can used to help track down spammers who disguise their IP address in decimal form.

The Subnet Calculator can list the CIDR aggregates for a range of IP addresses or classful networks. Two IP addresses separated by a hyphen form an IP address range (example: 192.111.4.0-192.111.15.0).

The Subnet Calculator can help you to recognize and use common IP address patterns or categories using the "Select Pattern" popup menu.

The network "Port" popup menu allows you to see the currently configured IP address for the selected port if any.

## IPv6 Features

The IPv6 Subnet Calculator extends many of the features above to cover 128-bit IPv6 addresses.

IPv6 addresses are often created from an underlying IPv4 or Ethernet MAC address and the Input box allows you enter these components directly or use the currently configured values from your system by selecting the corresponding network port.

The "Select Pattern" popup displays a list of common IPv6 address categories you can use to build a desired address, and the Description field along the bottom of the window identifies the category and sub components of any IPv6 address entered.

The Compress/Expand popup menu allows you to view IPv6 addresses in compresed or expanded form.

The Subnet area can be used to view and configure sub networks.

## Additional Features

When you invoke one window from another, the corresponding data is automatically transferred.

A popup menu keeps a list of Recent Targets or history pre-loaded with some common values based on your network configuration. The contents of the target field are added to the list when a test to that target is invoked. If the recent targets menu becomes full (10 entries), the least recently used item will be removed. To add or remove an item, or clear the entire list, use the corresponding selections from the History menu.

You can open and use multiple Subnet Calculator windows at the same time.

The previous IPv4 Only Subnet Calculator is still available by pressing the Option key while selecting the Subnet Calculator tool from the tool menu or launcher palette.

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