When doing my exercise i was asked : how many useable subnets and hosts will the following network address allow?
Network address 172.31.0.0/29
The choices were between :
A. There 7 useable subnets with 30 useable host addresses
B. There 7 useable subnets with 2046 host addresses
C. There 7 useable subnets with 8190 useable host addresses
D. There 8 useable subnets with 30 useable host addresses
E. There 8 useable subnets with 2046 useable host addresses
F.There 8 useable subnets with 8190 useable host addresses
The answer the book's author gives is F but I answered C.
considering we have 13 host bits, that leads to 2^13 minus 2=8190 and the 3 subnet bits give 2^3 minus two reserved , thus 6 subnets. But we're allowed for using zero subnet, so one can have 7 subnets.
Can also we use the broadcast subnet number?
I will pass the CCNA exam next week, what will i answer if the question want me to tell how many subnets are useable, given n subnets bits? (2 power n minus 2 or not?)