Hi there,

I want to divide a private network in to subnets (common enough). We
are currently using 192.168.1.* for the whole network, no subnets.

I want to expand the space and have three subnets with up to 2000 hosts
on each.

Can I use 192.168.[1-8].* for the first, 192.168.[9-16].* for the
second etc, with a 255.255.248.0 netmask?

I know that 192.168.*.* is a Class C which is traditionally /24 but I
also know that classful subnets are deprecated. So is /21 okay for
192.168.*.* ?

Also, on principles: each subnet should be the same size (netmask),
correct?

Thanks for all advice.

David.

davidjxyz@gmail.com wrote:
> I want to expand the space and have three subnets with up to 2000 hosts
> on each.
>
> Can I use 192.168.[1-8].* for the first, 192.168.[9-16].* for the
> second etc, with a 255.255.248.0 netmask?
>

I think you mean 192.168.[0-7].* and 192.168.[8-15].*

> I know that 192.168.*.* is a Class C which is traditionally /24 but I
> also know that classful subnets are deprecated. So is /21 okay for
> 192.168.*.* ?

As long as the router that interconnects the subnets supports classless
routing (CIDR: classless inter-domain routing), as any modern router
should. Although even with a classful router you could probably
configure a static route for each class C network.

> Also, on principles: each subnet should be the same size (netmask),
> correct?

With VLSM/classless routing the subnets don't need to be the same size.
Using the same address space above you could do something like:

192.168.0.0/21 2046 hosts
192.178.8.0/22 1022 hosts
192.168.12.0/23 510 hosts
192.168.14.0/24 254 hosts
192.168.15.0/25 126 hosts
192.168.15.128/25 126 hosts

for a total of six subnets or varying sizes.

> I think you mean 192.168.[0-7].* and 192.168.[8-15].*

Yes. Silly mistake.

Thanks for the reply. That clears it up tremendously.

On 25 Mar 2006 09:18:59 -0800, davidjxyz@gmail.com <davidjxyz@gmail.com> wrote:
| Hi there,
|
| I want to divide a private network in to subnets (common enough). We
| are currently using 192.168.1.* for the whole network, no subnets.
|
| I want to expand the space and have three subnets with up to 2000 hosts
| on each.
|
| Can I use 192.168.[1-8].* for the first, 192.168.[9-16].* for the
| second etc, with a 255.255.248.0 netmask?
|
| I know that 192.168.*.* is a Class C which is traditionally /24 but I
| also know that classful subnets are deprecated. So is /21 okay for
| 192.168.*.* ?
|
| Also, on principles: each subnet should be the same size (netmask),
| correct?


Sorry if this turns out to be a duplicate. The previous try looks like
it failed from this end.


Using a /21 netmask is OK, but the suggested subnets you gave are all
identical.

To be in different subnets, IP addresses must be different within the
first x bits of the address, where 'x' is the number in the subnet mask.

The list of /21 subnets in 192.168.0.0 starts with:

192.168.0.0/21
192.168.8.0/21
192.168.16.0/21

and so on, with the 3rd octet increasing by 8 each time. There will be
32 of these subnets, ending with

192.168.248.0/21


I hope this s.


--
Reverend Paul Colquhoun, ULC. http://andor.dropbear.id.au/~paulcol
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