Class

Range

Formula

Default Mask

A

0-127

N.H.H.H

255.0.0.0

B

128-191

N.N.H.H

255.255.0.0

C

192-223

N.N.N.H

255.255.255.0

 

1.  Determine the Class of an address.

2.  Determine How many bits you must borrow (if applicable).

3.  Determine the possible and usable nuber of subnets.

2(B) 2 = Usable Subnets

4.  Determine the possible and usable number of hosts.

2(U) 2 = Usable Hosts

5.  Determine the Default Mask.

6.  Determine the Subnet Mask

7.  Determine the increment. (Increment = Possible Number of Hosts)

8.   Determine the Network and broadcast address for each subnetwork.