> Another question, What is the
difference between DHCP and AutoIP?
DHCP involves a server supplying the client with an IP
address, subnet mask, gateway and other configuration parameters (e.g. DNS is
almost always supplied). The client may supply an identification
string. The server is responsible for picking the appropriate IP address,
which it might do by allocating from a pool of available addresses, or
assigning a fixed address based on the client's ID or MAC address.
AutoIP (also known as APIPA for "Automatic Private IP
Addressing") is a mechanism where a device assigns itself a random IP address
from a particular range reserved for AutoIP (169.254.0.0/16). No server is
involved.The subnet mask used is always 255.255.0.0, there is no gateway,
and it doesn't have any other configuration parameters such as
DNS.
After picking a random AutoIP address, the device polls
the network to check whether that address is already in use by something else.
If it is, then the device picks another random IP address and tries
again.
AutoIP is often used in ad hoc networks which are
temporarily set up between two or more devices, e.g. you could use it when
you plug a laptop into an embedded device via a direct Ethernet cable. If
both devices use AutoIP then they will be able to talk to each other. Actually
finding each other may require something like sending a broadcast ping, or using
a name-based service advertising and discovery protocol like SLP, NetBIOS or
Apple's Bonjour (multicast DNS, with DNS service discovery).