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TOPIC: Subnetting Guidelines - I thought I had it but?

Subnetting Guidelines - I thought I had it but? 6 years 3 months ago #35248

  • Waves
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Hi this is my first post so hello to all.

What a great site which is really filling in some gaps in my knowledge, so thank you.

I was reading the subnetting tutorial and thought I had finally understood this subject until I got to the "Subnetting Guidelines" section.
What are the maximum number of hosts on a given segment?

You must ensure that there are enough bits available to assign host
addresses to the organization’s largest subnet.
If the largest subnet needs to support 40 host addresses today, 2 to the power of 5 =
32 will not provide enough host address space, so you would need
to round up to 2 to the power of 6 = 64.

If I understand correctly (which I probably don't) doing the above (2 to the power of 6 = 64) would only allow 2 hosts per subnet and 64 subnets.

To allow enough for 40 hosts on a class c network would you not have 2 to the power of 2 giving 4 subnetworks with 62 hosts on each.

I've re read the tutorial and can't get my head round this bit could you please explain where I'm going wrong, thanks again for a great site.
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Re: Subnetting Guidelines - I thought I had it but? 6 years 3 months ago #35252

  • KiLLaBeE
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Hi Waves,
The '6' in the example is specifically referring to the HOST bits in the subnet, which would leave us with '2' which would give you 4 subnets (2^2). So in the end, you would have four subnets, each with 64 addresses, but only 62 out of the 64 being usable.

Maybe if the example stated exactly how the 6 bits would be used (network or host) then it would have been more clear.

So if we had a class C network of 192.168.0.0 255.255.255.0, then the end result after subnetting would be:

192.168.0.0-63
192.168.0.64-127
192.168.0.128-191
192.168.0.192-255

In my above example, the beginning address is the network and the ending address is the broadcast. But as you can see, we have 4 subnets and 62 usable addresses in each.
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Re: Subnetting Guidelines - I thought I had it but? 6 years 3 months ago #35257

  • Waves
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Ah I thought the 6 bits were subnet bits rather than host bits, I now get it. Thanks for making that clear to me KiLLaBeE.
:D
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