Ip Address Calc

IP Address Calculator

Montgomery College, Maryland Fall 2013 NW252

Classfull IP Addresses

• Classfull IPv4 addresses use Classes A,B or C ranges • Class A subnet mask is 255.0.0.0 • Class B subnet mask is 255.255.0.0 • Class C subnet mask is 255.255.255.0 • Three easy steps:

– Find the subnet number – Find the broadcast address – Find range of valid IP addresses

For academic purposes only 2

Classfull IP Addresses

• Example:

– Class A IP address: 11.120.40.10

Octet ->

Address Subnet mask First address Broadcast address Last address 11 255 11 11 11

1

120 0 0 255 255

2

40 0 0 255 255

3

10 0 1 255 254

4

For academic purposes only

3

Classfull IP Addresses

• Example:

– Class B IP address: 172.16.20.30

Octet -> Address Subnet mask 172 255 1 16 255 2 20 0 3 30 0 4

First address

Broadcast address Last address

172

172 172

16

16 16

0

255 255

1

255 254

4

For academic purposes only

Classfull IP Addresses

• Example:

– Class C IP address: 193.168.200.5

Octet -> Address Subnet mask First address Broadcast address 193 255 193 193 1 168 255 168 168 2 200 255 200 200 3 5 0 1 255 4

Last address

193

168

200

254

5

For academic purposes only

Classless IP Addresses - VLSM

• Example:

– IP address: 172.16.21.30 – Subnet mask 255.255.252.0

• Let’s:

– First find the subnet number (‘key’ number) – Work with a ‘magic’ number – Find the broadcast number using the ‘magic’ number – Find the range of valid IP addresses.

For academic purposes only 6

Classless IP Addresses - VLSM

IP address: 172.16.21.30/255.255.252.0

Find the subnet number: -Identify in the subnet mask the number that is not 255 nor 0. This is the ‘key’ number -To the left of the key number copy the values from the IP address -To the right of the key number enter 0 (zero) In this example the subnet number (key number) is: 252 (not 255 nor 0)

Octet -> Address

Mask Subnet First address Broadcast address

1 172

255 172...