Subnetting question

gouki2005

Question: You are designing a subnet mask for the 172.31.0.0 network. You want 12 subnets with up to 3100 hosts on each subnet. What subnet mask should you use?
Answer: 255.255.240.0


ok i know how to get the hosts



255.255.255.255 so i need 12 bits to get 4096 so thats why i have this mask so my new mask is /20 now because the 172.31.0.0 is a class b subnet so the number of subnets are 16-20 = 4 and 4^2 = 16 so i have enough to supplie the 12 subnets


i am right?

Essendon

Yes you are right. This is the method I use too.