Appendix C
Subnetting Class A
Class A subnetting is not performed any differently than subnetting with Classes B and C, but there are 24 bits to play with instead of the 16 in a Class B address and the 8 in a Class C address.
Let’s start by listing all the Class A masks:
255.0.0.0 (/8) 255.128.0.0 (/9) 255.255.240.0 (/20) 255.192.0.0 (/10) 255.255.248.0 (/21) 255.224.0.0 (/11) 255.255.252.0 (/22) 255.240.0.0 (/12) 255.255.254.0 (/23) 255.248.0.0 (/13) 255.255.255.0 (/24) 255.252.0.0 (/14) 255.255.255.128 (/25) 255.254.0.0 (/15) 255.255.255.192 (/26) 255.255.0.0 (/16) 255.255.255.224 (/27) 255.255.128.0 (/17) 255.255.255.240 (/28) 255.255.192.0 (/18) 255.255.255.248 (/29) 255.255.224.0 (/19) 255.255.255.252 (/30)
That’s it. You must leave ...