Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 315
DHCP Messages

The following message types are used with client/server interaction:

•  DHCPDISCOVER : This is a client broadcast that is used to locate available servers. It may be forwarded by routers to allow for server segments.

•  DHCPOFFER : This is a server-to-client response to a DHCPDISCOVER message with an offer of configuration parameters.

•  DHCPREQUEST : This is a client message to servers for:

•  Requesting offered parameters from one server and implicitly declining offers from all others.

•  Confirming correctness of previously allocated addresses, (e.g., system reboot).

•  Extending the lease on a particular network address.

•  DHCPACK : This is a server-to-client message that contains configuration parameters, including a committed network address.

•  DHCPNAK : This is a server-to-client message indicating the client’s notion of network address is incorrect (e.g., client has moved to new subnet) or a client’s lease has expired.

•  DHCPDECLINE : This is a client-to-server message indicating a network address is already in use.

•  DHCPRELEASE : This is a client-to-server message relinquishing a network address and canceling the remaining lease.

•  DHCPINFORM: New with RFC 2131, this is a client-to-server message asking only for local configuration parameters; the client already has an externally configured network address.