It is theoretically possible to develop software for client-machines that finds an unused address by picking them out of the blue and broadcasting a request of all the other client machines to see if they are using them. Appletalk is designed around this idea, and Apple’s MacTCP can be configured to do this for IP. However, this method of IP address assignment has disadvantages.
- A computer that needs a permanently-assigned IP number might be turned off and lose its number to a machine coming up. This has problems both for finding services and for security.
- A network might be temporarily divided into two non-communicating networks while a network component is not functioning. During this time, two different client-machines might end up claiming the same IP number. When the network comes back, they start malfunctioning.
- If such dynamic assignment is to be confined to ranges of IP addresses, then the ranges are configured in each desktop machine rather than being centrally administered. This can lead both to hidden configuration errors and to difficulty in changing the range. Another problem with the use of such ranges is keeping it easy to move a computer from one subnet to another.