DHCP(7) 						 Miscellaneous Information Manual						   DHCP(7)

NAME

       DHCP, dhcp - Dynamic Host Configuration Protocol (DHCP) introductory information

DESCRIPTION

       The  Dynamic  Host  Configuration  Protocol  (DHCP)  enables you to automatically assign IP addresses to clients on networks from a pool of
       addresses.  The IP address assignment and configuration occurs automatically whenever appropriate client systems (workstations and portable
       computers)  attach  to  a  network.   The  Tru64 UNIX implementation of DHCP is based on the JOIN product by JOIN Systems, Inc.	(JOIN is a
       trademark of JOIN Systems, Inc.)

       Using DHCP has the following advantages: Automates IP address administration Provides central configuration of network computers Eliminates
       duplicate IP addresses Supports older style BOOTP (on clients only)

   DHCP Environment
       DHCP  is  based	on  the client-server model, in which client systems request resources from other systems called servers.  A server is any
       host system or process that provides a network service. A client is any host system or process that uses services from a server.

       A single host, or server, can provide more than one service.  Servers are passive; they do not call clients, they wait for clients to  call
       them.

       The client always initiates the DHCP request.  The server answers the request, subject to its own configuration rules.

   DHCP Software
       The  DHCP  software contains the following components: Daemon programs that handle communications between the server (joind) and the client
       (joinc) A graphical user interface program (xjoin) that sets up the dynamic DHCP databases Configuration  files	that  contain  information
       needed to start the DHCP daemons Administrative commands, such as programs that enable you to configure and maintain DHCP

       The  following  sections  briefly describe these components.  For additional information, see the Network Administration guide and the JOIN
       Server Administrator's Guide.  The latter is provided by JOIN Systems, Inc. in HTML format, and it can be accessed by opening the following
       file with a web browser: /usr/doc/join/TOC.html

   DHCP Daemons
       On the Tru64 UNIX system, the DHCP daemons (joind and joinc) reside in the /usr/sbin directory. The following sections describe the daemons
       and their tasks.

   The joind Daemon
       The joind DHCP server daemon performs the following tasks: Reads the /etc/bootptab configuration file and the  /etc/join/server.pcy  policy
       file.   Listens for client hosts requesting BOOTP or DHCP information.  Responds to each client with an Internet address and other informa-
       tion that allows the client to boot and configure its TCP/IP stack.  Supports both BOOTP and DHCP requests  making  the	bootpd	daemon	no
       longer necessary on the server.

   The joinc Daemon
       The  joinc DHCP client daemon performs the following tasks: Reads the /etc/join/client.pcy policy file.	Starts the DHCP protocol handshake
       if requested to configure an interface.	Sends a request to the broadcast address for the network or subnet.  Receives configuration infor-
       mation,	configures  and  brings  up  the  interface, and then sleeps in the background until it needs to renew the lease.  Brings down the
       interface if it cannot renew a lease.

   The xjoin Graphical User Interface Program
       The xjoin graphical user interface program resides in the /usr/bin/X11 directory, and enables you to configure the DHCP server and  set	up
       the DHCP dynamic databases.

   DHCP Configuration Files
       The  /etc/bootptab  file  contains entries for DHCP and BOOTP clients.  You add, delete, and modify entries in this file by using the xjoin
       program.  The entries are then used by the joind server daemon to configure the DHCP and BOOTP clients.

       The following table describes additional DHCP configuration files that reside in the /etc/join directory:

       ------------------------------------------------------------------------
       File	    Function
       ------------------------------------------------------------------------
       client.pcy   Governs the behavior of a DHCP client
       namepool     Specifies names for dynamic host name assignment

       netmasks     Contains an entry for each netmask that is other than the
		    standard A, B, or C masks
       nets	    Specifies the networks to administer with the joind daemon
       server.pcy   Governs the behavior of a DHCP server
       ------------------------------------------------------------------------

       The client.pcy and server.pcy files contain information about remote systems contacted by DHCP, the devices used to contact these  systems,
       the  times  to contact the systems, and the level of access that remote systems can have to the local system.  You must edit the client.pcy
       file using an editor.  You modify the server.pcy file by using the xjoin program.  Configuring these files is optional.

       The other files are configured by using the xjoin program.

   Database Files
       Starting with DHCP Version 2.3.n, DHCP database files are stored in a new format, one that is incompatible with older formats.	An  online
       document  explains the reasons behind this change, lists the files that are affected, and provides instructions for converting the files to
       the new format.	The document, README-DB237, and a conversion utility, conv185-237, are located in the /etc/join directory.

   Administrative Commands
       The following table lists the DHCP administrative commands and their functions.	These commands are used by joind, joinc, or xjoin, and are
       not typically run by administrators.

       -------------------------------------------------------------------------------
       Command	  Function
       -------------------------------------------------------------------------------
       bptojdb	  Converts bootptab entries into static IP entries for JOIN databases
       checkdba   Checks the JOIN IP address lease database for internal consistency
       dhcpcemu   Emulates a DHCP client
       dhcpconf   Controls invocation of DHCP on the client
       dhcpparm   Prints client DHCP parameters
       jdbdump	  Dumps fields from the DHCP dynamic databases
       jdbmod	  Adds, modifies, or deletes data in the DHCP dynamic database
       jdbreg	  Registers hosts in the DHCP dynamic databases
       jdpshow	  Displays the contents of a specific JOIN server database
       probenis   Checks for the existence of a NIS server on the network
       shleases   Displays a client's IP address leases
       showdbs	  Displays the contents of the server's dynamic database
       showdhc	  Displays a client's configuration files
       showhash   Dumps raw hash table contents for debugging use
       showtree   Dumps raw binary tree contents for debugging use
       -------------------------------------------------------------------------------

RESTRICTIONS

       A cluster member should never be a DHCP client. It should always use static addressing.

       If  a  cluster  is  to  support	a  DHCP server, there can be only one DHCP server for all the cluster members using a common database with
       failover.

RELATED INFORMATION

       Commands: bptojdb(8), checkdba(8), dhcpcemu(8),	dhcpconf(8),  dhcpparm(8),  jdbdump(8),  jdbmod(8),  jdbreg(8),  jdbshow(8),  probenis(8),
       shleases(8), showdbs(8), showdhc(8), xjoin(8)

       Daemons: joinc(8), joind(8)

       Files: bootptab(4) client.pcy(4), dhcptags(4), namepool(4), netmasks(4), nets(4), server.pcy(4)

       Technical Overview, Network Administration, JOIN Server Administrator's Guide (/usr/doc/join/TOC.html), /etc/join/README-DB237 delim off

																	   DHCP(7)