Subnet Planning Question

[Kevin Longley]

My network is presently configured to use the 192.168 private ip address
range with a subnet mask of 255.255.255.0. This basically allows a maximum
of 254 host addresss's. I can foresee that within a few years I may exceed
that amount of host address's. I can't foresee needing more than around 500
ip address's for hosts so my question is this:

Should I reconfigure the subnet mask, dhcp scopes, etc. in the private ip
address range of 192.168 to allow for around that amount of address's and
therefore leave my options open should I need to have a routed network or is
it really a non issue since there are other private ip address ranges that
could be used? I am running a switched network for all nodes so that traffic
is a not an issue. Presently support about 125 devices. All opinions
welcome.

 

[Phillip Windell]

Leave the mask as is. Just add new subnets in the third octet, you'll have
254 hosts per each one, so two subnets will give you the 500 hosts you
mentioned. But just choose them carefully. Remember that if you ever use a
site-to-site VPN between your network and someone else's that you do not end
up both running the same addresses in your private networks. Consult
everyone you think that might ever happen with and make sure that you all
avoid duplicating addresses. For example we have over 20 sister stations
connected by VPN and so I contacted our Corp HQ and got a list of the
subnets that all the sites used and picked an unused one and then let our HQ
know which one I was going to use.

It is a good idea to keep the number of host per subnet to around 300 or
less, but that is not a "hard" number, you can go higher than that. It
really depends on what you actually do on the system more so than just
simply how many machines there are on it.