Re: subnetting
hi ya irvine
your table is correct... at least the ones i saw ( *.128, *.192 masks)
that was wrong in the original that i could calculate in my hand in a
second..
- its "powers of 2" as each bit in the mask is added/deleted
c ya
alvin
On Sun, 13 Jan 2002 irvine.russell@edu.hel.fi wrote:
>
> Hello all,
>
> I am a little confused about subnetting. I read an article
> in the linux journal. I later bought a book and it seems to
> give quite a different picture of subnets.
>
> First a quote from the book:
> Debian GNU/Linux 2.1 Unleashed
>
> ----snip-----
>
> When subnetting, it's important to note that the subnetworks
> that have the address with all zeros and all ones are invalid.
> So, in the previous example where we divided the 8-bit host
> address into a 3-bit subnet address and 5-bit subnet address,
> we will only be able to have 6 subnetworks instead of the 8 that
> we might have expected because '000' and '111' are invalid
> subnetwork addresses...
>
> Table 16.2 Subnets inside a Class C Network
>
> Netmask Usable Subnets Hosts per Subnet Total Hosts
>
> 255.255.255.0 1 254 254
> 255.255.255.128 0 127 0
> 255.255.255.192 2 62 124
> 255.255.255.224 6 30 180
> 255.255.255.240 14 14 196
> 255.255.255.248 30 6 180
> 255.255.255.252 62 2 124
> 255.255.255.254 127 0 0
>
> ----snip-----
>
> As far as I understood the following is correct.
>
> Netmask Usable Subnets Hosts per Subnet Total Hosts
>
> 255.255.255.128 2 126 252
> 255.255.255.192 4 62 248
> 255.255.255.224 8 32 240
> 255.255.255.240 16 14 224
> 255.255.255.248 32 6 192
> 255.255.255.252 64 2 128
>
> I haven't needed to worry about such matters in practice, but I
> wanted to know which is correct.
>
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