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Please enter a IP adress and a prefix.

A prefix can be entered as subnet mask (net mask in classless mode).

A prefix shows network portion bits length from head of an IP address.

For instance, the bits from first bit to 24th bit shows network number portion and the other 8 bits ( from 25th bit to 32th bit) shows host number portion, when prefix is 24.

A prefix can be represented as a subnet mask ( net mask in classless addressing) . All network number portion bits of subnet mask are 1 and all host number portion bits of it are 0. Normally subnet mask is represented as decimal number of each 8 bits in case of IPv4.

Both of the prefix value and the subnet mask value are updated when a prefix or a subnet mask is entered in this App.

Please do the below operations.

-Tap the round rectangle button under the IP address label.

  (then, specially designed keypad is shown)

-Enter a IP address on the keypad.

-Tap the "Done" button on the keypad.

Please do the below operations.

-Tap the "C" button on the keypad.

-Tap the "Done" button on the keypad.

Also, the IP address can be cleared using AC button.

(AC buttion is available on version 2.0) 

Please do the below operations.

-Tap the round rectangle button under the prefix label. 

  (then, the prefix picker is shown)

-Select value on the prefix picker.

  (then, the prefix value and the subnet mask value are set)

-Tap the red round X button on prefix picker to Close it.

You can enter the prefix on the keypad when the prefix switch is ON. 

The . (period) button is changed to the /(slash) button when 4 octets were entered if the prefix is ON. 

Please select the "None" on the prefix picker.

Also, the prefix can be cleared using AC button.

(AC buttion is available on version 2.0) 

Please do the below operations.

-Tap the round rectangle button under the subnet mask label. 

  (then, the subnet mask picker is shown)

-Select value on the subnet mask picker.

  (then, the subnet mask value and the prefix value are set)

-Tap the red round X button on subnet mask picker to Close it.

Please select the "None" on the subnet mask picker.

Also, the subnet mask can be cleared using AC button.

(AC buttion is available on version 2.0) 

This App enables "Done" button on the keypad in the below case.

- The IP address field is empty.

- all 4 octets were entered.

-The prefix was entered. 

This App disables the prefix button and the subnet mask button when "class D" or "class E" address is set because subnet mask and prefix are not used in "class D" or "class E" address.

These buttons are enabled when you clear IP address.

The below chart shows class of IP addresses.

This App changes items on pickers. And changes depend on class of the IP address.

A shorter subnet mask than a default mask of each class is invalid. Therefore, This App shows only valid items for each class.

This App supports classless addressing on version 2.0.

Please tap the gear icon to change addressing mode when you calculate classless address.

The version 2.0 supports 31 bits prefix because a subnetwork that has 31 bits prefix can be used for point-to-point link based on RFC3021. 

The 32 bit mask shows host route and it may be used in links using PPP encapsulation but This App doesn't accept the /32 bit mask because calculation is not required for it.