1. /20
11111111.00000000.00000000.00000000
11111111.11111111.11110000.00000000

2. /20
255.255.240.0
base2 | 2^7 | 2^6 | 2^5 | 2^4 | 2^3 | 2^2 | 2^1 | 2^0 | | Decimal | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | Binary | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 240 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |

3. /20
12 bits in host portion. (2n-2)
212-2=4094

4. /21
11111111.00000000.00000000.00000000
11111111.11111111.11111000.00000000
255.255.248.0
base2 | 2^7 | 2^6 | 2^5 | 2^4 | 2^3 | 2^2 | 2^1 | 2^0 | | decimal | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | Binary | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 248 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
11 bits in host portion. (2n-2)
211-2=2046

5. /22
11111111.00000000.00000000.00000000
11111111.11111111.11111100.00000000
255.255.252.0
base2 | 2^7 | 2^6 | 2^5 | 2^4 | 2^3 | 2^2 | 2^1 | 2^0 | | decimal | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | Binary | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 252 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
10 bits in host portion. (2n-2)
210-2=1022

6. /23
11111111.00000000.00000000.00000000
11111111.11111111.11111110.00000000
255.255.254.0
base2 | 2^7 | 2^6 | 2^5 | 2^4 | 2^3 | 2^2 | 2^1 | 2^0 | | decimal | 128 | 64 | 32 | 16 | 8 | 4 | 2 | 1 | Binary | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 255 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | | 254 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
9 bits in host portion. (2n-2)
29-2=510

7. /24
11111111.00000000.00000000.00000000
11111111.11111111.11111111.00000000
255.255.255.0
base2 |