DHCP(7)DHCP(7)NAME
DHCP, dhcp - Dynamic Host Configuration Protocol (DHCP) introductory
information
DESCRIPTION
The Dynamic Host Configuration Protocol (DHCP) enables you to automati‐
cally assign IP addresses to clients on networks from a pool of
addresses. The IP address assignment and configuration occurs automat‐
ically 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 trade‐
mark of JOIN Systems, Inc.)
Using DHCP has the following advantages: Automates IP address adminis‐
tration 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 pro‐
grams that enable you to configure and maintain DHCP
The following sections briefly describe these components. For addi‐
tional information, see the Network Administration: Services 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 information
that allows the client to boot and configure its TCP/IP stack. Sup‐
ports 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 broad‐
cast 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 inter‐
face 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 pro‐
gram. The entries are then used by the joind server daemon to config‐
ure 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.
SEE ALSO
Commands: bptojdb(8), checkdba(8), dhcpcemu(8), dhcpconf(8), dhcp‐
parm(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), net‐
masks(4), nets(4), server.pcy(4)
Technical Overview, Network Administration: Services, JOIN Server
Administrator's Guide (/usr/doc/join/TOC.html), /etc/join/README-DB237
DHCP(7)
