x.x.x.x/N
T=32
N=given
H=T-N
n=N-default
h=8-n
2^n=total subnets
2^h=increment of subnet numbers
2^H=total nodes in each subnet=increment


/20 --> 20 1's in the subnet mask
11111111.11111111.11110000.00000000
3rd octet <--- octet of interest
n=4 --> 2^n = 16 subnets
h=4 --> 2^h = 16 (*256) hosts in each subnet --> increment (range)
0,16,32,48,64,80,96,...,240

172.16.0.0
172.16.16.0
172.16.32.0
172.16.48.0
...

10000000 = 128
11000000 = 192
11100000 = 224
11110000 = 240
11111000 = 248
11111100 = 252
11111110 = 254
11111111 = 255

/23 = 255.255.254.0
/20 = 255.255.240.0
/19 = 255.255.224.0

10.128.32.64/12
/12 = 255.240.0.0
T=32 (total 32 bits)
N=13 (given)
H=19 (T-N=19)
n=4  (N-default)
h=4  (1111 0000, 4 0's, or 8-n)
increment = 2^h = 2^4=16
10.0.0.0
10.16.0.0
...
10.128.0.0
10.143.255.255
..
10.240.0.0/12


10.1.1.1/29
/29 = 255.255.255.248.0
T=32
N=29
H=3
n=29-8=21
h=3
increment = 2^h = 8 = range
10.0.0.0
10.0.0.7
10.0.0.8
...
10.1.1.0
1001.1.7
10.1.1.8
...
10.255.255.248
10.255.255.255

subnets = 2^n = 2^21