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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)            9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)                 9  TCP/IP Dynamic Host Configuration Protocol (DHCP)                      9  DHCP Configuration and Operation

DHCP General Operation and Client Finite State Machine 1 2 3 DHCP Lease Reallocation Process

Dealing With Lost Messages or Failure of the Allocation Process

You can see in this description that there are a number of situations that may occur that require a client to retransmit messages. This is because DHCP uses UDP which is unreliable and can cause messages to be lost. If retransmissions don't fix a problem such as not receiving a DHCPOFFER or a DHCPACK from a server, the client may have to start the allocation process over from scratch. The client must include enough “intelligence” to prevent it from simply trying forever to get a lease when there may not be a point—for example, if there are no DHCP servers on the network, no number of retransmissions will help.

Thus, after a number of retries the client will give up and the allocation process will fail. If the client is configured to use the Automatic Private IP Addressing feature, this is where it would be used to give the client a default address. Otherwise, the client will be, well, “dead in the water”.

DHCP General Operation and Client Finite State Machine 1 2 3 DHCP Lease Reallocation Process