
Start with 128 then divide by 2 for each value 
Reverse the order of the Bit Values 
= Subnets  2 
= Bit Value  2 
= Cumulative Sum of Bit Value 
= Total Bit Value 
=24 + Bits Borrowed 

Borrowed Bits 
Bit Value 
Subnets 
Usable Subnets 
Usable Hosts 
Total Bit Value 
Subnet Mask 
Network Bits 
1
 128
 2 
0 
126 
128 
255.255.255.128 
/25 
2
 64
 4
 2
 62
 192
 255.255.255.192
 /26 
3
 32
 8
 6
 30
 224
 255.255.255.224
 /27 
4
 16
 16
 14
 14
 240
 255.255.255.240
 /28 
5
 8
 32
 30
 6
 248
 255.255.255.248
 /29 
6
 4
 64
 62
 2
 252
 255.255.255.252
 /30 
7
 2
 128
 126
 0
 254
 255.255.255.254
 /31 