# 172.16 network question

I'm pretty bad with IP design.   is there a 172.16 /12 network? If so,  how many subnets and hosts I can do?
planning how many offices,  larger and smaller I can put there.
Thanks bunch.
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Alpha GeekCommented:
The three "private" ranges are:

10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.32.255.255
192.168.0.0 - 192.168.255.255

"172.16 /12" Translates to 172.16.0.0 - 172.32.255.255, so you could use this addressing scheme. You could have over a million hosts.

Usual practice is to create smaller subnets, often implemented as VLANS. Commonly, /24 networks are used, which permit 4096 subnets, each with 254 hosts. You could however choose other ways of dividing the address space up. Maybe 2048 subnets of 510 hosts or whatever, or 1024 of 1022.
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Commented:
"172.16 /12" Translates to 172.16.0.0 - 172.32.255.255, so you could use this addressing scheme. You could have over a million hosts.
172.16.0.0 - 172.31.255.255
;)
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Sr. Network EngineerCommented:
To answer the question, how many subnets and how many hosts per subnet, is a function of where you subnet the initial scope 172.16.0.0/12.

If you leave the mask at default (/12), then the prior answers are correct, you will have 1,048,574 host and one network. If you change the mask to /16 you will have 16 networks wit 65,536 hosts each. If you change the mask to /24 you an get 4,080 networks with 253 hosts each.

The simpler way to go about the process is to determine the number of networks you need or if more appropriate, determine the max hosts you want to drop into any particular subnet, and then work the math backwards to determine the missing component.

There are other considerations that need to be taken into account to get a solid answer but the above is a sufficient starting place.

Hope that helps
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Commented:
If you change the mask to /16 you will have 16 networks wit 65,536 hosts each. If you change the mask to /24 you an get 4,080 networks with 253 hosts each.
16 networks wit 65,534 hosts each. If you change the mask to /24 you an get 4,096 networks with 254 hosts each.
:)
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Sr. Network EngineerCommented:
Yes Predrag, thank you for correcting for the network and broadcast IDs.  The point remains the same.
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