Subnet mask conversion:
- Subnet masks can be written as 32-bit binary numbers, but not just any binary number.
- The value must not interleave 1s and 0s.
- If 1s exist, they are on the left.
- If 0s exist, they are on the right
Converting between binary and prefix masks:




SUBNETS:

EXAMPLE:
consider the case of IP address 8.1.4.5 with mask 255.255.0.0
1) 255.255.0.0 = /16, so P=16
2) 8.1.4.5 is class A network so network bits are N=8
3) S = P – N = 16 – 8 = 8
4) H = 32 – P = 32 – 16 = 16
5) 2 to the power of 16 – 2 = 65534 hosts/subnet
6) 2 to the power of 8 = 256 subnets

EXAMPLE 2:
consider address 200.1.1.1, mask 255.255.255.252
1) 255.255.255.252 = 24 + 6 = /30
2) 200.1.1.1 = class C network, so N = 24
3) S = P – N = 30 – 24 = 6
4) H = 32 – 30 = 2
5) 2 to the power of 2 – 2 = 2 hosts
6) 2 to the power of 6 = 64 subnets
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