I need to divide a network
172.16.0.0/12 into 3 different subnets for different purposes. One of them needs 6 host addresses, another 85 host addresses and the last 100 host addresses. It should be done so that as few addresses as possible goes unused.
Now, the first subnet is easy, I can make a subnet
172.16.0.0/29 which has 23 - 2 = 6 usable host addresses. I'm not sure how to approach the next subnet though. Is it possible to make a subnet from say
172.16.0.8-172.16.0.127? And perhaps continuing with the third from
128-255 (last octet)?
My second guess would be to divide the smallest subnet as before, then make the next subnet at
172.16.0.1/25 and the last at
172.16.0.2/25. This way the amount of unused addresses would be higher, though.
I should also mention that the subnets should have access to the Internet. How can this be assured? I read that the whole
172.16.0.0/12 address range is private and thus they do not work in the Internet. Is this true?
EDIT: This was what I had in mind:
I understand that I cannot subnet my network in the same way they have done here because two of my subnets has to reserve an address space of 128 hosts. This means that I could create subnets
172.16.1.0/29. What I am wondering now is: does the space in "reserved for future use" count as some sort of subnet, or can they be used as normal addresses?