networking - Subnetting/Supernetting Configuration

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I have an existing network.
It looks like this.

Router LAN (192.168.0.1 /24)
-> Switch (192.168.0.10 /24) -> Workstations (192.168.0.100 - 192.168.0.200
/24)

Our network has expanded and I need to have
more hosts available.

The simplest way to do
this is to change the router's inside interface subnet (/24) to a supernet
(/23).

This will give me
192.168.0.0-192.168.1.254 instead of just
192.168.0.0-192.168.0.254.

That is
exactly what I want.

My question is
do I need to adjust the subnet masks on hosts on either the 192.168.0.0
/24 network or 192.168.1.0 /24 network or should they continue to work having only
changed the subnet mask on the inside interface of the
router?

The reason I'm confused
is 192.168.0.0 /24 and 192.168.1.0 /24 are both part of 192.168.0.0 /23 so in my mind
there is not a need to change the subnet masks of hosts in those smaller networks but
having made the subnet mask change only to the inside interface of the router I am not
able to communicate with a host with the static IP address
192.168.1.40.

Finally, I would
like to know if I need to change the subnet mask on the hosts, the switches, or
both.

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class="normal">Answer

If you do
this, then yes, you will need to change the netmask of all the hosts connected to the
network, otherwise you will get annoying problems like hosts in different networks not
being able to communicate. The ethernet-level method of contacting a host differs
according to whether the destination host is on the same network or not, the netmask is
used to determine whether this is the
case.

The good news is that it only
applies to communication between hosts in different (old or new) parts of the network.
You can change the netmask on the router, then on all of the hosts, and then start
adding hosts in the new part of the network.

If
reconfiguring all the hosts is cumbersome, I would add a second IP
(192.168.1.1/24) to your router's inside interface. Communication between the two
networks would (at least to some extent) go through the router's inside interface, so if
you plan to have a massive amount of communication between hosts in your network you may
not want that. You could instead add something bigger, like 172.16.0.0/16, and gradually
move over your computers from the old
network.

You might want to investigate DHCP,
especially if some part of your hosts are user machines that usually do not need to be
contacted.