On what basis are IP numbers allocated?
If your question is about ip address allocation by isp:
whenever a user connect to the isp's network, from a specified
range, its server allocates a dynamic ip address mostly or it can
be static. if it is static, then the user will have the same ip
address for a very long time (based on the deal). But if it is
dynamic then it means it will change after some time or upon
now the if your question is about your LAN (at work etc):
a computer again can have a fixed ip address assigned by the
administrator or dhcp server can give your PC an ip address upon
start. You may retain the same ip address for some days if such
permission has been granted by the admin.
IP addresses in LAN are normally not public addresses and
therefore the range may not matter as long as it is in the same