of 22
8/14/2019 dhcp-wp
1/22
901 San A ntonio Road
Palo Alto, CA 94303
1 (800) 786.7638
Sun Microsystems, Inc.
1.512.434.1511
Dynamic Host Configuration
Protocol
Technical W hite Paper
8/14/2019 dhcp-wp
2/22
Please
Recycle
Copyright 2000 Sun Microsystems, Inc.,901 San Antonio Road, Palo Alto, California 94303U.S.A.All rights reserved.
This prod uct or docum ent is protected by copyrigh t and distributed und er licenses restricting its use, copying, distribution, and d ecompilation.
No part of this produ ct or documen t may be reprod uced in any form by any means without pr ior written authorization of Sun and its licensors,
if any.Third -party software, including font technology,is copyrigh ted and licensed from Sun sup pliers.
Parts of the prod uct may be derived from Berkeley BSD systems, licensed from the University ofCalifornia. UNIXis a registered trad emark
in the U.S. and oth er countr ies,exclusively licensed through X/ Open Compan y,Ltd.
Sun, Sun Microsystems, the Sun logo, Solaris, and Solstice PC-Admin are tradem arks, registered trademarks, or service marks of Sun
Microsystems,Inc. in the U.S. and oth er count ries.All SPARC trademark s are used un der license and are trademark s or registered trademark s
of SPARC International, Inc.in the U.S. and other countr ies.Prod ucts bearing SPARC trademarks are based upon an architecture developed by
Sun Microsystems, Inc.
The OPEN LOOK and Sun Graph ical User Interface was developed by Sun Microsystems,Inc. for its users and licensees.Sun acknow ledges
the pioneering efforts ofXerox in researching and d eveloping the concept of visual or graphical user interfaces for the compu ter industry. Sun
hold s a non -exclusive license from Xerox to the Xerox Graph ical User Interface, wh ich license also covers Sun s licensees who imp lemen t OPEN
LOOK GUIs and oth erwise comply with Suns written license agreements.
RESTRICTED RIGHTS : Use, du plication, or d isclosure by th e U.S. Govern men t is subject to restrictions of FAR 52.227-14(g)(2)(6/ 87)
and FAR 52.227-19(6/ 87), or DFAR 252.227-7015(b)(6/ 95) and D FAR 227.7202-3(a).
DOCUMENTATION IS PROVIDED AS IS AND ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES,
INCLUD ING AN Y IMPLIED WARRANTY OF MERCHAN TABILITY, FITNESS FOR A PARTICULAR PURPO SE OR NON -
INFRINGEMENT, ARE DISCLAIMED, EXCEPT TO THE EXTENT THAT SUCH DISCLAIMERS ARE HELD TO BE LEGALLY INVALID.
Copyright 2000 Sun Microsystems, Inc.,901 San Antonio Road, Palo Alto, Californie 94303Etats-Unis. Tous droits rservs.
Ce produit ou docum ent est protg par un copyrigh t et distribu avec des licences qui en restreignent lutilisation, la copie, la distribution, et
la dcomp ilation.Au cune partie de ce produit ou documen t ne peu t tre reprod uite sous aucun e forme, par quelqu e moyen que ce soit, sans
lautorisation p ralable et crite de Sun et de ses bailleurs de licence, sil y en a. Le logicield tenu p ar des tiers, et qui compren d la technologie
relative aux polices de caractres,est p rotg par u n copyright et licenci par d es fournisseurs de Sun .
Des parties de ce produ it pourron t tre drives des systmes Berkeley BSD licencis par lUniversit de Californie.UN IXest une m arque
dp ose aux Etats-Unis et dans dautres pays et licencie exclusivemen t par X/ Open Comp any,Ltd .
Sun, Sun Microsystems, le logo Sun , Solaris, et Solstice PC-Adm in sont des marqu es de fabrique ou des marqu es dposes, ou marqu es de
service,d e Sun Microsystems, Inc.a ux Etats-Unis et dan s dautres pays. Toutes les marqu es SPARC sont utilises sous licence et sont des
marqu es de fabrique ou d es marques dp oses de SPARC Interna tional, Inc.a ux Etats-Unis et dans dautres pays. Les prod uits portan t les
marqu es SPARC sont bass sur une architecture dvelopp e par Sun Microsystems,Inc.
Linterface dutilisation graphiqu e OPEN LOOKet Sun a t dveloppe pa r Sun Microsystems, Inc.p our ses utilisateurs et licencis. Sun
reconnat les efforts de pionn iers de Xerox pour la recherche et le dveloppem ent du concept des interfaces dutilisation visuelle ou grap hique
pou r lindu strie de linformatiqu e. Sun dtient u ne licence non exclusive d e Xerox sur linterface dutilisation grap hique Xerox,cette licence
couvran t galement les licencis de Sun qu i mettent en place linterface dutilisation grap hique OPEN LOOK et qui en outre se conforment aux
licences crites de Sun.
CETTEPUBLICATION EST FOURNIE EN LETAT ET AU CUNE GARANTIE, EXPRESSE OU IMPLICITE, NEST ACCORDEE, Y COMPRIS
DES GARANTIES CONC ERNANT LA VALEUR MARCHANDE, LAPTITUDE DE LA PUBLICATION A REPON DRE A UNE UTILISATION
PARTICULIERE, OU LE FAIT QUELLE NE SOIT PAS CONTREFAISANTE DE P RODUIT DE TIERS. CE DENI DE GARAN TIE NE
SAPPLIQUERAIT PAS, DANS LA MESURE OU IL SERAIT TENU JURIDIQUEMENT NUL ET NON AVENU.
8/14/2019 dhcp-wp
3/22
Contents
Introduction .................................................................................................1
What Is DHCP? ..................................................................................1
History of DHCP ................................................................................3
Where DHCP Is Useful .......................................................................4
Why DHCP Is Important ....................................................................5
Suns Implementation of DHCP .................................................................6
DHCP Implementation in the Solaris 8 Operating Environment .......6
Interoperability with Other Operating Environments .........................7
Key DHCP Improvements in the Latest Release ................................8
Client Implementation ................................................................................9
Using DHCP to Install Software .........................................................9
Using DHCP for Diskless Clients .......................................................10
DHCP Administration Using the DHCP Manager .....................................11
DHCP Directions ........................................................................................14
IETF Activities ...................................................................................14
Enterprise DHCP Service ...................................................................14
Name Service Integration ...................................................................15
DHCP for IPv6 ....................................................................................16
Conclusion ..................................................................................................17
References ...........................................................................................18
8/14/2019 dhcp-wp
4/22
1
CHAPTER 1
Introduction
The phenomenal growth of the Internet over the past several years has driven the
acceptance of the TCP/ IP protocol suite (the basic comm un ication stand ard of the
Internet) into corporate n etworks. Corporations trad itionally utilized a myriad ofdifferent protocols, how ever, the TCP/ IP environm ent h as emerged to become
dom inant w ithin most organizations because it enables corporations to comm un icate
more effectively and utilize Intern et tools to increase efficiency.
The design of TCP/ IP requires that every system u sing the p rotocol have a un ique
add ress that fits into the ad dressing scheme w ithin the organization. Therefore,
every add ress must be a mem ber within a subn et mad e up of a group ing of logically
associated computers.
One way to make system management simpler and less expensive is to move the
management of the IP1
add resses away from the client systems and onto centralized
servers. In response to this need, the Internet Engineering Task Force (IETF) created
th e Dynamic Host Configuration Protocol (DHCP).
What Is DHCP?
DHCP u ses a client/ server relationship to allocate ad dresses, track their usage, and
reclaim a p redetermined list of IP ad dresses and other configuration information
shared in a n etwork of systems. Each organization has one or m ore DHCP servers
with a ran ge of predefined IP add resses, as well as other startup information or
add itional param eters. When a u ser boots a client system, that system broadcasts
a request for a DHCP server to issue it an IP add ress.
1. IP is the Internet Proto col layer of the TCP/ IP comm un ication stack defined by the Inter net Engineer ing TaskForce (IETF).
8/14/2019 dhcp-wp
5/22
2 Dynamic Host Configuration Protocol White Paper
In the most common situation, the DHCP server responds with an IP address and
a specified p eriod of time (called a lease) for w hich the client m ay u se that ad dress.
By using DHCP technology, network m anagers m ove the configuration of netw ork-related param eters to a centralized DH CP server, wh ich is m uch m ore cost-effective
from a management standpoint. DHCP manages the assignment and reclamation of
an organizations IP address nam espace, freeing n etwork ad ministrators to
concentrate on other tasks. Figure 1 dep icts a typical DHCP environm ent.
FIGURE 1 Topology of common DHCP client/ server environment.
DHCP m ay also be used to p ass add itional information to a booting system. First,
a client issues a boot requ est, which includ es sp ecific configuration information
about th e client. The server receives this information packet and compares the
configuration information to a databa se of possible parameters, respond ing with
additional data beyond the IP address (such as time zone or department-specific
information).
IP addresses are normally divided into two types, static an d dynamic. A static IP
address is permanently assigned to a client, which means that the addresses and
associated p arameters d o not change betw een system startup s (reboots). They are
often loaded into the startup information from the system d isk of that ma chine,
although they can also be supplied by a remote server. A dynamic address is not
assigned to a client until it is booted an d g iven the ad dress by a server. Where theadd ress is not sup plied to the client until system startup , DHCP is the protocol of
choice.
BOOTP RelayAgent
BOOTP RelayAgent
Boot/Root/InstallServer
172.21.00 172.22.00
172.20.00
8/14/2019 dhcp-wp
6/22
Introduction 3
Systems that export services (print, file, Web, mail, etc.) are not particularly well-
suited to DHCP client usage because changing ad dresses ma ke it difficult to find
these systems and complicate host-based access controls. Servers can use staticassignment with a lease to consistently have DHCP issue the same address each
time the server b oots. This allows the centralized m anagem ent of configuration
parameters, even if the system is not using dynamic addresses.
History of DHCP
Historically, the assignm ent of Internet ad dresses to h ost ma chines required
adm inistrators to manua lly configure each machine and man ually keep track of IP
add ress assignments. While this is sufficient for small netw orks w ith a few system s,
the overhead of manually managing a sites address name space becomes
prohibitively expensive as the nu mber of hosts increases.
DHCP w as developed from an earlier protocol called Bootst rap Protocol (BOOTP),
wh ich w as used to pass information d uring initial booting to client systems. The
BOOTP stand ard was originally released in 1985 based on w ork by John Gilmore of
Sun Microsystems and Bill Croft of Stanford University. It allowed diskless clients
(systems w ithout an y d isk) to store configuration d ata in a centralized server. The
BOOTP standard was d esigned to store and up date static information for clients,
including IP addresses.
The BOOTP server always issued the sam e IP add ress to the same client. As a result,
while BOOTP addressed the need for central management, it did not address the
problem of managing IP addresses as a dynamic resource.
To add ress the need to m anage d ynam ic configuration information in general, and
dynamic IP addresses specifically, the IETF standardized a new extension to BOOTP
called Dyn amic Host Configura tion Protocol, or DH CP. DHCP servers u tilize
BOOTP packets, with DHCP-specific flags an d data, to convey information to the
DHCP clients.
To stand ardize th e DH CP environm ent, the IETF issued a series of RFCs focused
on DH CP extensions to the BOOTP technology. The most recent of these stand ards
is RFC 2131, which was issued in March 1997. DHCP is still an area of active
developm ent and it is reasonable to assume that th ere will be add itional RFCs
related to the DHCP environment. Sun is working with other vendors to ensure
that DHCP continues to be a standard supp orted by a large number of vendors.
8/14/2019 dhcp-wp
7/22
4 Dynamic Host Configuration Protocol White Paper
Where DH CP Is Usefu l
The most common u sage of DHCP is to move the mana gement of IP add resses away
from the distributed client systems and onto one or more centrally man aged servers.
These central servers maintain da tabases of parameter information (add resses,
netmasks, etc.), eliminating the n eed for clients to store static network information
on their machines. This specifically obviates the need to configure TCP/ IP
parameters into client machines. Since most client systems now ship from the factory
with d ynam ically assigned IP add resses as the default configura tion, the u ser need
only boot the machine to be up and run ning w ith the TCP/ IP protocol. This
approach saves time configuring or debugging the network environment, thereby
redu cing th e cost of ownership for client systems.
DHCP is particularly useful in the following en vironments:
s Sites that have man y m ore TCP/ IP clients than network adm inistrators. By u sing
DHCP, man agers can more effectively man age a large commu nity of clientsystems.
s Sites where laptops comm only move am ong n etworks w ithin the site. By using
DHCP, laptop users can plu g into the network at any location an d u se a local
DHCP-assigned IP add ress to comm un icate with the local systems.
s Sites that have fewer available TCP/ IP ad dresses than they h ave clients that need
them. Typically, this occurs in dial-up situations, such as an Internet service
provider (ISP) environment, w here there is a large commu nity of potential users,
but on ly a small percentage of them are online at any given time. Here, DHCP is
used to issue the IP add ress to a client machine at the conn ection time, allowing
the DHCP server to reu se the same ad dress once the current client ha s logged off.
Most ISPs have m oved to this app roach to redu ce their need for scarce Internet
addresses.
s Sites that frequ ently need to mov e the location of services from host to host. Since
DHCP delivers the location of services, moving services from one machine to
another and changing the appropriate DHCP configuration information means
that any DHCP client will automatically pick up the change withou t the
administrator having to make a trip to the user's machine.
s Sites that sup port d iskless clients. More details on this use of DHCP are provid ed
in the Client Implementation section.
s Any combination of the above.
8/14/2019 dhcp-wp
8/22
Introduction 5
Why DH CP Is Imp ortant
According to a nu mber of stud ies, the largest contributor to th e total cost of
compu ting is the adm inistration of distributed clients. These stud ies, wh ich
focus on the cost of ownership for enterprise clients, ind icate that the best w ay
for corporations to redu ce the cost of distributed comp uting is to move the
adm inistration of their client systems to centralized m anagem ent servers. DHCP can
play an imp ortant role in redu cing the cost of ownership for large organizations by
shifting the job of man aging n etwork configuration information from client systems
to remote management by a small pool of system and network managers.
It is becoming increasingly difficult for organ izations to acqu ire add itional Internet
add resses. Corporations m ust often justify the requirement for these additional
add resses through a long a nd sometimes difficult process of needs definition. DHCP
helps red uce the imp act of the increasing scarcity of available IP add resses in tw o
ways.
First, DHCP can be used to m anage the limited nu mber of stand ard, routable IP
add resses that are available to an organization. It does this by issuing the ad dresses
to clients on an as needed basis and reclaiming them when the addresses are no
longer required. When a client needs an IP add ress, the DH CP server will issue an
available address, along with a lease period during which the client may use the
add ress. When the client is done with the add ress (or when th e lease on the add ress
expires), the ad dress is pu t back in a pool and is available for the next client seeking
an add ress.
Second, DHCP can be used in conjun ction w ith Netw ork Ad dress Translation (NAT)
to issue private netw ork ad dresses to connect clients (throu gh a N AT system) to the
Internet. The DH CP server will issue an add ress to the client that w ill not route,
such as 192.168.*.* or 10.*.*.*2
The client will use a N AT system as th egateway machine, which packages up the request with the permanent address of the
NAT system. When the resp onse comes back from the Internet, the NAT server will
forward th e packet back to the client. DHCP enables this to be done w ithout taking
up valuable routable add resses and m akes certain that all clients use consistent
parameters, such as subnet masks, routers, and DNS servers.
2. Ad dr esses in th e ran ge of 10.*.*.*, 172.16.*.*th rou gh 172.31.*.*, and 192.168.*.*ar e de fined by IETF RFC 1918as being reserved for private intranets and are not routed to th e Internet.
8/14/2019 dhcp-wp
9/22
6
CHAPTER 2
Suns Implementation of DHCP
Sun began shipp ing DH CP in 1994 as p art of its Solstice PC-Admin
produ ct, and
integrated it into the Solaris
Operating Environment in version 2.6. In th e latest
release of the Solaris 8 Op erating Environmen t, Sun has significantly improvedthe functionality of DHCP software, ma king it one of the best in the ind ustry.
DHCP Implementation in the Solaris 8 Op erating
Environment
The Solaris Operating Environm ent imp lementation of the DHCP environmen t is
consistent w ith the p hilosophy of traditional UNIX
utilities in that it is simple to
use, yet flexible enough to be ap plied across a w ide variety of different tasks. A
system ad ministrator can u tilize this flexibility to solve a n en tire range of netw ork
and system configura tion issues.
A good example of the flexibility of the Sun environmen t is the u se of macros.
Macros, wh ich ma y be thoug ht of as containers of configuration d ata, are keyword s
that the system manager can define to prompt the DHCP server to respond with
specific configuration information. For example, a keyword might be the architecture
of the client, such as IA32_Solaris. When the DH CP sees this keyw ord in one of
the configura tion request pa ckets, it respond s with th e network location of the
Solaris Operating Environment x86 boot server.
Macros may be used in many different roles depending on the needs of the
organization. They m ay be u sed to tran sfer d epartm ental- or perhap s locale-specific
information (such as time zone) to the client. Macros may also be layered so that one
macro can call a series of add itional m acros. Since they can p oint to other m acros,
it is possible for common macros to be targeted by man y other m acros.
8/14/2019 dhcp-wp
10/22
Suns Implementation of DHCP 7
Sun s DH CP server imp lementation allows th e association of configuration
parameters with macros that are:
s Specific to a clients type (regardless of where it is located in the enterprise)
s Specific to the clients netw ork
s Specific to th e client itself
s Specific to the address
s Any combination of the above
This scoping hierarchy is a useful tool that enables adm inistrators to organize
their configuration data where needed.
The Sun DHCP server is designed to allow scaling u p to the size of a network
consisting of thousan ds of client systems. As stated previously, the DHCP packets
are built on top of the BOOTP packet protocol. Since BOOTP packets are commonly
passed over rou ter links, it is possible for an entire corporation to be serviced by asmall num ber of centralized DHCP servers.
Interoperability with Other Operating
Environments
Since Suns DHCP client and server technology is built in compliance with IETF
RFC 2131, it works transp arently with DH CP technology built by other vend ors,
provided they also comp ly with RFC 2131. This stand ard is clearly defined an d
commonly imp lemented, so that Sun DHCP software generally interacts seamlessly
with DH CP software from oth er compan ies. In add ition, Sun tests interoperability
with other vendors on an ann ual basis during the vend or-neutral Connectathonevent (ww w.connectathon.org). While Sun cannot w arrant the sp ecific
implementations of other vend ors, the Sun DHCP generally interoperates
well with versions from other m ajor vend ors.
The DHCP server ship ping w ith the last few versions of the Solaris Operating
Environment can act as a server to Solaris software-based clients, most Microsoft
Wind ows clients, clients from other UNIX vendors, Macintosh clients, and a nu mber
of other netw ork clients. Many curren t ISPs are successfully using the Sun DHCP
server to sup port large nu mbers of Microsoft Window s and Macintosh clients.
8/14/2019 dhcp-wp
11/22
8 Dynamic Host Configuration Protocol White Paper
Key DH CP Imp rovements in the Latest Release
Sun has a long history with DH CP. As previously noted, the first Sun DHCP
implementation was part of the Solstice PC-Admin layered product and was
designed to help ma nage PC clients by using a system with the Solaris Operating
Environment as a m anagem ent system. The first version of DHCP that shipp ed
directly with th e Solaris Operating Environment w as includ ed in v ersion 2.6.
Keeping with Sun's history of continual product upgrades, Sun has made some
major improvem ents in th e Solaris 8 Operating Environm ent release.
To begin with, a new DH CP Manager p ackage has been included that u tilizes
several new wizards and visual tools that make the DHCP environmen t mu ch easier
to man age. Where the earlier releases of DHCP required the m odification of control
files to manag e the environmen t, many of these adm inistration tasks hav e been
simplified by the inclusion of a series of easy-to-use tools. More details on these
enhan cements will covered in the DHCP Administration using the DHCP Managersection.
A new configuration protocol option has been ad ded for the Solaris 8 Operating
Environment n etwork installation. In ad dition to the traditional Sun RARP/ RPC
Bootparam s configuration mod el, DHCP configuration is now a sup ported
installation op tion. Choosing DHCP configuration over RARP/ RPC Bootparam s
frees adm inistrators from the requirement to h ave a boot server or an install server
on every network . Note that the selection of a configuration protocol is an either/ or
selection; no combination of the protocols is possible.
With th e Solaris 8 Operating Environment, Sun n ow offers full-featured DH CP
functionality in one easy-to-administer pa ckage.
8/14/2019 dhcp-wp
12/22
9
CHAPTER 3
Client Implementation
DHCP can be used to provide parameters above and beyond those required for
network commu nication, such as par ameters need ed for remote installation of the
Solaris Operating Environmen t on client systems.
Using DHCP to Install Software
DHCP can be used to help system administrators build or configure new software
onto netw ork-attached systems. This could take the form of a gen eric installation of
software on a d isk that need s to be custom ized by the DH CP server. Alternatively, it
could be a totally empty d isk that will be configured an d bu ilt du ring installation
using a remote source for the operating system. Either way, the DHCP server is used
to store the configuration information so that wh en the system is booted for the first
time, the DHCP server w ill provide all the configuration information requ ired by the
client for the bu ilding of software.
For this type of system, DHCP may b e used in conjun ction w ith the Solaris
Operating Environm ent install server to autom atically build th e operating system
on the client, includ ing all of the p arameters u nique to th is system. Throug h this
method, the end user need only plug the computer in and p ower it on to build a
fully customized environmen t, includ ing an operating system and layered p rodu cts.
This method of software installation helps reduce the administration burden and
cost of ownership for the client systems.
8/14/2019 dhcp-wp
13/22
10 Dynamic Host Configuration Protocol White Paper
Using DHCP for Diskless Clients
It is sometimes beneficial to configure an environmen t to includ e d iskless systems.
The primary reasons to use d iskless systems are to lower client costs by not
requiring the use of disk drives and increase management and security through
the central storage of application programs and user data.
In highly secure environments, such as classified government installations, as well as
some equally guarded environments outside of the government, the ability to store
data locally presents a security issue. Diskless workstations can be u sed to ensu re
that there is no data stored outside of the file server system man aged by the
institutions MIS departm ent.
When th ere is no local storage (beyond the limited requirements of the bootstrap
chips), a DH CP server can store the entire configuration for the booting of any
number of diskless clients. Each system has a Media Access Control (MAC)3
address
that is stored on the Ethernet card. In add ition, many system s have the ability to
store a limited am oun t of information in th e bootstrap EPROMs (e.g., system
architecture and p referred nod e name). This information can be passed to the DHCP
server in the exchan ge of packets between th e DHCP server and the client d uring
the booting process. These packets, in turn, can be used to promp t the DHCP server
to respond with som e of the information stored in ma cros on the server. The
information can be generic to all systems or can be targeted to a specific node.
The macros can either contain all the configuration information that a system
wou ld need to boot or point to a location in the netw ork for that information.
Note th at m acros also allow scoping by platform typ e (for examp le SUNW.Ultra-1).
This feature is used to ensu re that the right operating system binar y is down loaded
to the correct p latform. With this cap ability, a system does not require local storage
to boot with an en tirely custom configuration u nique to this system, which obviatesthe need for any local storage.
3. The MAC addres s is used in layer 2 of the OSI model to give the Ethern et card access to the med ia witho uthigh er levels or layers of software.
8/14/2019 dhcp-wp
14/22
11
CHAPTER 4
DHCP Administration Usingthe DHCP Manager
Historically, the w ay a DHCP server is configured is similar to the trad itionalmethod of managing systems, through Comm and Line Interface (CLI) utilities.
While these utilities will continue to be su pp orted in future releases, Sun ha s raised
the bar by making the DHCP environment even easier to manage.
The DHCP server in the Solaris 8 Operating Environm ent comes with a series
of wizard ap plications that enab les the DHCP server to be easily configured by
answ ering a simple set of questions. Once these questions have been answ ered, the
data is stored in the traditional configuration files. This provid es a system man ager
with the best of both worlds.
For examp le, if the ad ministrator wou ld like to continue to use the CLI comm and s,
or has d eveloped sp ecial scripts to man age the env ironment for the specific needs of
the organ ization, these tools will still work. If the adm inistrator is looking for an
easier and m ore intuitive interface, the Sun DHCP Man ager software includ es thewizards and GUI-based tools to make the environment easy to manage.
Figure 1 shows the DH CP Manager using a w izard-type interface to add a new en try
into the range of add resses that the DHCP server can issue. The instructions on
the left part of the screen gu ide the u ser through the p rocess. The p oint-and -click
interface makes it very easy for the adm inistrator to enter and display all of the d ata.
8/14/2019 dhcp-wp
15/22
12 Dynamic Host Configuration Protocol White Paper
FIGURE 1 Add ing a new entry to the range of addresses using a wizard.
In the p revious section, DHCP Implementation in the S olaris 8 Operating Environment,
there is a description of how m acros can be u sed to help m anage comp lex DHCP
environmen ts. Figure 2 shows h ow th e DHCP Man ager simplifies the process of
maintaining m acros and the associated d ata using a GUI interface to display and
upd ate data for the mktserv macro. Whenever this macro is passed to the DHCP
server, all of the associated op tion names an d op tion values are returned to the
client. The contents section of the screen can be u sed to add , delete, or chang e any
of the data stored within the macro.
FIGURE 2 Macro information is displayed/ updated through an easy-to-use interface.
8/14/2019 dhcp-wp
16/22
DHCP Administration Using the DHCP Manager 13
The DHCP Manager is used to manage a range of client addresses and names in
Figure 3. Notice that a single manager session can be used to man age the d atabase
for mu ltiple boot servers. In this examp le, clients of both chicopee an d mktserv arebeing man aged concurren tly. While an ad dress is actively in use, the DHCP Man ager
tracks the current lease expiration and MAC ad dress of the system using the
add ress. The man ager also tracks the macros currently associated w ith each client.
FIGURE 3 Network ad dresses and related information are easily reviewed and up datedthrough a graphical interface.
By using th e DHCP Manag er wizard a pp lications and GUI-based interfaces,
organizations can redu ce the complexity of installing the DH CP server environmen t
and lower the cost of managing the network environment.
8/14/2019 dhcp-wp
17/22
14
CHAPTER 5
DHCP Directions
Sun continues to invest in DHCP and over time, plans to includ e these investments
as further enha ncements to the p rodu ct set. This section d escribes some areas wh ere
Sun is currently focusing engineering efforts.
IETF Activities
The IETF is continually looking for wa ys to im prove DHCP software. As th ese
improvements are standardized through future RFCs, Sun will evaluate the
functionality of all imp rovements for p otential inclusion in future p rodu ct releases.
Sun is an active mem ber of the IETF developmen t in the DHCP w orking group , and
is helping to define new features of the p rotocol that will benefit Sun s customers.
Enterprise DHCP Service
Future versions of Sun s DHCP software m ay continue to be scaled u p to larger
computing environments. Enhancements might include a single DHCP server
that could support a customer's entire enterprise-wide organizational needs.
One of the best w ays to increase the p erformance of server app lications is to
improve th e mu ltithreading capability of the software. Multithread ing allows a
compu ting system to execute m ultiple copies of the application in an a synchronou s
fashion. In a traditional single-threaded application, each client must wait in line for
any previous requests to be fully satisfied before the server starts on the next clients
request. When there are mu ltiple processors and th e app lication ha s shared
resources that need to be controlled by the ap plication, a single-threaded task can
only run on a single processor, negating the ad vantage of multiprocessor servers.
8/14/2019 dhcp-wp
18/22
DHCP Directions 15
When a server application has been written to support hot mu ltithreading, each
client request is spaw ned off into an other thread -based set of instructions that can
potentially be run in p arallel on another processor. This capability can d ramaticallyincrease the scalability of a single server system to concurrently handle a significant
nu mber of clients.
A new, dynam ic object interface has been defined that allows su pp ort for new
data storage services to be added , including su pp ort for Oracle, Sybase, and other
databa se packages, withou t changing the DH CP service itself. Shared objects which
export this pu blic interface are known as public modules. If a new p ublic modu le is
add ed, and the DH CP service will locate it and offer it as a da ta storage alternative.
Since the API is pu blic, third parties are encouraged to write their own mod ules.
Public modu les written for such enterprise d atabases as Oracle and Sybase w ill offer
customers considerable flexibility regarding w here they store their DHCP d ata.
Some choices, such as datab ases, will offer higher capacity and potentially faster
performance. Customers hav e a choice of which modu le meets the particular needsfor their site. Since the p ublic modu le interface mu st be MT-safe, the DH CP server
will realize higher performan ce through th e use of a threading m odel. The DH CP
Manager will be updated so that transferring DHCP data from one public module-
sup ported service to another w ill be an easy task.
Future versions of the DHCP server may include add itional mu ltithreading su pp ort,
allowing the server to man age a m uch larger comm un ity of clients. Potentially,
a single server will be able to hand le the DHCP requ irements of an enterprise
consisting of many thousan ds of clients.
Name Service Integration
In the current DHCP env ironment, the DHCP server issues the IP add resses, wh ile
a separate name server stores the names associated with the network addresses.
DHCP assigns Internet add resses from a pool, often p lacing a client in a sp ecific
subn et. How ever, the actual add ress assigned to a nod e may app ear to be rand om in
natu re. The nam e of a client system in the n ame server is tied to the Internet add ress,
but the DHCP server and the name server do not currently coordinate between the
nam e of a node and its address. Therefore, the nam es that are issued to client
systems app ear rand om as w ell. If the client suggests a n ame, the suggestion
is ignored .
8/14/2019 dhcp-wp
19/22
16 Dynamic Host Configuration Protocol White Paper
In a soon-to-be-released up date to DH CP software, wh en a client requ ests a nam e,
the DHCP server will communicate with the name server in an attempt to ensure
that the requ ested client system n ame is issued to the client. The name server w illcheck to see if the requ ested n ame is currently in u se. If the nam e is available, the
nam e server will associate the actual add ress issued to the client w ith the requested
nam e. If the nam e is not ava ilable, the DHCP server w ill create a similar un used
nam e and will issue it to the client. Whatever nam e is actually issued to th e client
system will be comm un icated back to the client, so that the system nam e and the
nam e server name are iden tical.
The name services that will likely be supported include DNS, NIS+, LDAP, and file-
based name resolution.
DHCP for IPv6
One attribute that has made DHCP popular with customers is that it enables an
organization to more carefully manage usage of limited IP addresses. Such limitation
is typically felt by cu stomers w ho are u sing Internet Protocol version 4 (IPv4).
In the n ear futu re, custom ers w ill begin u sing the Internet Protocol version 6 (IPv6),
where a 128-bit addressing scheme should provide ample addresses for future
requirements. While this may seem to redu ce the need for DH CP, the requirement
for dynam ic configuration information du ring software installation an d system b oot
will continue long after IPv6 is in general u se.
A future release of the Sun DHCP environment may include support for
commu nication ov er the IPv6 protocol. This will allow DH CP to p rovide
concurrent boot capabilities for both IPv4 and IPv6 clients.
8/14/2019 dhcp-wp
20/22
17
CHAPTER 6
Conclusion
The Dynam ic Host Configura tion Protocol enables an organization to better control
its comp uting env ironment. In pa rticular DHCP can be used to mana ge IP add resses
in an environment where these addresses are in short supply. When there areenoug h ad dresses, DHCP also can be u sed to m ove the assignment of TCP/ IP
configuration information aw ay from the client systems an d on to the server, wh ere
it may be centrally managed.
DHCP can be used to configure m ore than just TCP/ IP information. It may be u sed
to store virtually any typ e of configuration d ata, including information u sed d uring
the installation of software or for storing system-specific param eters for d iskless
nodes. All of these uses move the management burden and cost for a distributed
environmen t awa y from the client systems (wh ere the cost of own ership is typically
most expensive) to the more cost-effective control of centralized servers an d their
system administrators.
The Solaris 8 Operating Environm ent includes m any en hancemen ts to earlier
releases of DHCP software from Sun . Management of the DHCP env ironment h asbeen made simpler through the use of an improved GUI interface and management
wizard s. Through these new tools, custom ers can use DHCP to ena ble remote
installation of software u sing stand ards-based tools, as well as continue to u se in-
house developed scripts or macros. These improvements have made Suns DHCP
server state of the art in the ind ustry. Custom ers thinking of implementing DH CP in
their organizations should p lan to use the Solaris 8 Operating Environmen t as the
platform for their DHCP env ironment.
8/14/2019 dhcp-wp
21/22
18
CHAPTER 7
References
s RFC 951 Bootstrap Protocol (BOOT P), Bill Croft, Stanford Univer sity, John
Gilmore, Sun Microsystems, September 1985
s RFC 1542 Clarifications and Ext ensions for t he Bootstrap Protocol, W. Wimer,Carn egie Mellon Un iversity, October 1993.
s RFC 2132 DHCP Options and BOOTP Vendor Extensions, S. Alexander, Silicon
Grap hics, Inc., R. Drom s, Buckn ell Univer sity, March 1997
8/14/2019 dhcp-wp
22/22
