RFC 3203 (rfc3203) - Page 2 of 6

DHCP reconfigure extension

RFC 3203               DHCP reconfigure extension          December 2001


2.1 Terminology

   DHCP client : host to be reconfigured using DHCP.

   DHCP server : server which configured the DHCP client.

2.2 Force renew procedures

   The DHCP server sends a unicast FORCERENEW message to the client.
   Upon receipt of the unicast FORCERENEW message, the client will
   change its state to the RENEW state, and will then try to renew its
   lease according to normal DHCP procedures.  If the server wants to
   assign a new IP address to the client, it will reply to the DHCP
   REQUEST with a DHCP NAK.  The client will then go back to the init
   state and broadcast a DHCP DISCOVER message.  The server can now
   assign a new IP address to the client by replying with a DHCP OFFER.
   If the FORCERENEW message is lost, the DHCP server will not receive a
   DHCP REQUEST from the client and it should retransmit the FORCERENEW
   message using an exponential backoff algorithm.  Depending on the
   bandwidth of the network between server and client, the server should
   choose a delay.  This delay grows exponentially as retransmissions
   fail.  The amount of retransmissions should be limited.

   The procedures described above assume the server to send a unicast
   FORCERENEW message to the client.  Receipt of a multicast FORCERENEW
   message by the client should be silently discarded.

   It can be that a client has obtained a network address through some
   other means (e.g., manual configuration) and has used a DHCP INFORM
   request to obtain other local configuration parameters.  Such clients
   should respond to the receipt of a unicast FORCERENEW message with a
   new DHCP INFORM request so as to obtain a potential new set of local
   configuration parameters.  Note that the usage of these procedures
   are limited to the set of options that are eligible for configuration
   by DHCP and should not override manually configured parameters.

   Note further that usage of the FORCERENEW message to reconfigure a
   client address or local configuration parameters can lead to the
   interruption of active sessions, and that as such these  procedures
   should be used in controlled circumstances.











T'Joens, et al.             Standards Track