From: Brian Hescock (bhescock@xxxxxxxxx)
Date: Sun Aug 06 2000 - 17:49:29 GMT-3
Harbir,
The way the documentatin showed it was rather confusing. There are
eight subnets of 32 ip's each (30 useable hosts each), starting from
subnet 0 through subnet 7. Subnet 7 would be from 192.168.5.224 through
.255. The answer Williams provides below is the rest of the explanation.
Brian
On Sun, 6 Aug 2000, William Swedberg wrote:
> Subnet 0 is the all zero subnet while subnet 7 is the all 1s subnet.
> When calculating subnets you use 2 to the nth minus 2. N being the number
> of subnet bits. And -2 being the all 0 and 1s subnets. In your example you
> get 2 to the 3rd - 2 giving you 8 - 2 = 6. By using the IP SUBNET-ZERO
> command you are now able to us the all 0 and all 1s subnets.
>
>
> William Swedberg CCNP CCDP
> ----- Original Message -----
> From: Harbir Kohli <harbirk@sympatico.ca>
> To: 'Ccielab <ccielab@groupstudy.com>
> Sent: Sunday, August 06, 2000 12:50 PM
> Subject: subnetting question
>
>
> > Hello all,
> >
> > What is the problem with using subnet 7 in the following:
> >
> > IP Subnet Calculation & Design
> >
> > --------------------------------------------------------------------------
> ---
> >
> > IP Class: C IP Address: 192.168.5.0
> > Mask Bits: 3 Subnet Mask: 255.255.255.224
> > Subnets: 6+1 IP Major Net: 192.168.5.0
> > Hosts/Subnet: 30 Major Net Bcast: 192.168.5.255
> >
> > Subnets for Fixed Length Subnet Masking
> > . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
> > . . .
> > No. Subnet Hosts Hosts Broadcast
> > Address From To Address
> >
> > 0 192.168.5.0 192.168.5.1 192.168.5.30
> > 192.168.5.31
> > 1 192.168.5.32 192.168.5.33 192.168.5.62
> > 192.168.5.63
> > 2 192.168.5.64 192.168.5.65 192.168.5.94
> > 192.168.5.95
> > 3 192.168.5.96 192.168.5.97 192.168.5.126
> > 192.168.5.127
> > 4 192.168.5.128 192.168.5.129 192.168.5.158
> > 192.168.5.159
> > 5 192.168.5.160 192.168.5.161 192.168.5.190
> > 192.168.5.191
> > 6 192.168.5.192 192.168.5.193 192.168.5.222
> > 192.168.5.223
> > 7 192.168.5.224 192.168.5.225 192.168.5.254
> > 192.168.5.255
> >
> > Don't use subnet 0 (unless using ip subnet-zero command) and subnet 7.
> > Address space wasted by subnetting = 29.13% ( 17.32% with ip
> > subnet-zero)
> > --------------------------------------------------------------------------
> ---
> >
> >
> >
> >
> >
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