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Hi,

What will happen if we use a class B subnet mask (255.255.0.0) on a
class C network such as (192.168.0.0)?


Thanks

jonnah wrote:
> Hi,
>
> What will happen if we use a class B subnet mask (255.255.0.0) on a
> class C network such as (192.168.0.0)?
>

Nothing. The concept of "classes" really went out the window when CIDR
was introduced. You may have to use the "ip classless" command. Your
question was Cisco related, I assume?

In article < >, jonnah888
@yahoo.com says...
> Hi,
>
> What will happen if we use a class B subnet mask (255.255.0.0) on a
> class C network such as (192.168.0.0)?

The network will blow up.

Nothing will happen. We now live in a CIDR world and classful mask
restrictions is a thing of the past. Unless you have WFWG in your
network, you'll be fine.


--

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In article < >,
(jonnah) wrote:

> Hi,
>
> What will happen if we use a class B subnet mask (255.255.0.0) on a
> class C network such as (192.168.0.0)?

This is called "supernetting" or "aggregation". It will treat the block
of networks as a single network for routing purposes.

--
Barry Margolin,
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***

Barry Margolin <> wrote in message news:<barmar->...
> In article < >,
> (jonnah) wrote:
>
> > Hi,
> >
> > What will happen if we use a class B subnet mask (255.255.0.0) on a
> > class C network such as (192.168.0.0)?
>
> This is called "supernetting" or "aggregation". It will treat the block
> of networks as a single network for routing purposes.

So my 192.168.0.0/24 network will essentially have 512 subnets with
65534 hosts per subnet using a /16 subnet mask?

In article < >,
jonnah <> wrote:
:Barry Margolin <> wrote in message news:<barmar->...
:> In article < >,
:> (jonnah) wrote:
:> > What will happen if we use a class B subnet mask (255.255.0.0) on a
:> > class C network such as (192.168.0.0)?

:> This is called "supernetting" or "aggregation". It will treat the block
:> of networks as a single network for routing purposes.

:So my 192.168.0.0/24 network will essentially have 512 subnets with
:65534 hosts per subnet using a /16 subnet mask?

No, if you configure your hosts as 192.168.0.0/16 then your
base reverved address will be 192.168.0.0, your broadcast address
will be 192.168.255.255, and everything else will be usable host space.
As long, that is, as all the other equipment involved agrees on it
being /16. You would, for example, run into trouble if you tried
to use RIP1 with this.

If you configure "ip classless" then you do not even have to worry
about "ip subnet-zero". CIDR does not reserve the first and last
subnets.
--
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