Most suitable Private IP ranges

[Col Shaw]

Hi,

We have 2 networks sepaerated by cisco routers, but they have been setup
with public IP address's instead of a private range. I am about to resolve
this issue but im wondering which would be the best range to use.

Lan1 has 2 servers 40 Workstations
Lan2 has 6 servers 150 Workstations (which is increasing by the day)

What i dont want to do is go through the process of changing the IP range to
find i could be short of available IP address's for Lan3

Any help/suggestions or examples would be very welcome.

 

[Phillip Windell]

These are the three RFC Private Ranges.

10.0.0.0 -- 10.255.255.255
172.16.0.0 -- 172.31.255.255
192.168.0.0 -- 192.168.255.255

My personal recommendation is to use something in the third group with 50 or
higher in the third octet to avoid the overused lower ones (0, 1, 2, ect)

192.168.51.0/24 Lan1 (254 hosts)
192.168.52.0/24 Lan2 (254 hosts)
192.168.53.0/24 Lan3 (254 hosts)
192.168.54.0/24 Lan4 (254 hosts)
192.168.55.0/24 Lan5 (254 hosts)
All masks are 255.255.255.0 as indicated by the "/24"

This way the last digit of the third octect gives you a mental "note" of
which Lan you are looking at. A 254 host subnet is a good clean size that is
a good high number but without being too overcrowded.

These are technically "whole" networks and are not really "subnets" because
there is no "splitting", but most people call them subnets just the same. If
you ever reach more than 254 host in one area then use two "networks" for
that one area.

 

[Jetro]

The possibility of IP scope shortage is easily avoided by using DHCP server.