Linux培训教程之一DHCP的安装和配置.docx
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Linux培训教程之一DHCP的安装和配置
Linux培训教程之一---DHCP的安装和配置
第一章DHCP的安装和配置
考虑大多数的情况，Linux作为DHCP服务器而windows95/98作为DHCP客户。
Linux也可以作为DHCP客户,即你要安装dhcpcdrpm软件包，Linux作为DHCP服务器，
只需要安装dhcpdrpm包（以Redhat6.1为例）
一．DHCP服务器工作的前提条件：
为了使DHCP服务器为windows机器服务，你可能需要创建一个到地址255.255.255.255
的路由，加这条路由命令到/etc/rc.d/rc.local使得每次启动后自动运行。
#routeadd-host255.255.255.255deveth0
如果报告错误消息：
255.255.255.255：
Unkownhost
试着加下面的入口到/etc/hosts文件
255.255.255.255dhcp,thentry:
#routeadd-hostdhcpdeveth0
二．DHCPd后台程序总是读取配置文件/etc/dhcpd.conf,下面给出一个DHCP配置文件的例子：
#Sample/etc/dhcpd.conf
default-lease-time1200;
max-lease-time9200;
optionsubnet-mask255.255.255.0;
optionbroadcast-address192.168.1.255;
optionrouters192.168.1.254;
optiondomain-name-servers192.168.1.1,192.168.1.2;
optiondomain-name"mydomain.org";
subnet192.168.1.0netmask255.255.255.0{
range192.168.1.10192.168.1.100;
range192.168.1.150192.168.1.200;
}
这将允许DHCP服务器分配两段地址范围给客户192.168.1.10-100或者192.168.1.150-200
如果客户不继续请求DHCP地址则1200秒后释放IP地址，否则最大允许租用的时间为9200秒。
服务器发送下面的参数给DHCP客户机：
用255.255.255.0作为子网掩码，用192.168.1.255作为广播地址，用192.168.1.254作为
默认网关，用192.168.1.1and192.168.1.2作为DNS服务器
如果你要为windows客户指定一个WINS服务器，你需要包括下面的选项到dhcpd.conf文件中：
optionnetbios-name-servers192.168.1.1;
三.你也能为某块网卡指定固定的IP地址，无论何时，这块网卡将总是从DHCP服务器获得
固定的IP地址：
加下面的语句到/etc/dhcpd.conf:
hosthaagen{
hardwareethernet08:
00:
2b:
4c:
59:
23;
fixed-address192.168.1.222;
}
也可连写为一行：
hostJephe{hardwareethernet00:
a0:
c9:
a6:
96:
33;fixed-address192.168.1.12;}
你也可为某台机器指定不同的网关地址，名服务器等：
hostJephe{hardwareethernet00:
a0:
c9:
a6:
96:
33;fixed-address192.168.1.12;option
routers192.168.11.5;}
四.大多数情况下，DHCP的安装不创建一个dhcpd.leases文件，在你启动DHCP服务器之前，
你必须创建空文件dhcpd.leases
#touch/var/state/dhcp/dhcpd.leases
为启动DHCP服务器，简单地打入/usr/sbin/dhcpd或者用#ntsysv把DHCP服务自动启动
这将启动dhcpd在eth0设备上，如果你想在eth1设备上启动dhcpd，则
#/usr/sbin/dhcpdeth1
如果为了调试DHCP，则用#/usr/sbin/dhcpd-d-f
五．两块网卡的情况：
有时你需要在一台安装了两块网卡（作防火墙或网关）的机器上安装DHCP服务，下面的例子
指出一台防火墙机器上的一种DHCP设置，因为对外的网卡（internet）不需要提供DHCP服务：
因此这样设置如下：
subnet192.168.1.0netmask255.255.255.0{
range192.168.1.2192.168.1.4;
default-lease-time86400;
max-lease-time259200;
optionsubnet-mask255.255.255.0;
optionbroadcast-address192.168.1.255;
optionrouters192.168.1.254;
optiondomain-name-servers192.168.1.254;
}
subnet202.102.34.102netmask255.255.255.255{
}
六．FAQ
a.为MAC机器固定IP地址？
当设置MAC机用DHCP功能获得IP地址后，如不知得到何地址，可在MAC机上发送一邮件出去，
收信者可通过mailheader检查发送者IP地址，而后ping该IP地址再利用arp命令检查arp
缓存中的该IP地址的对应物理地址。
b.若LAN上有windows机器装上了某DHCP功能的软件，如sygate,wingate之类，则可能
其他windows客户会优先去寻找windowsDHCP服务器，而不是LinuxDHCP服务器
参考材料：
附录：
在Redhat5.2中的DHCP配置（）
ConfiguringDHCPAndDNSServices
SetupLinuxtoallocateIPaddressandactasanameserver
SettingupDHCPonRedHat
Ifyournetworkhasalargenumberofclients,manuallyconfiguringeverymachine
withastaticIPaddressisatoughjob.TheDynamicHostConfigurationProtocol
（DHCP）letsyouautomaticallyassignanIPaddresstoamachineonthenetwork
fromapoolorrangeofIPaddressesithas.
ToconfigureaDHCPserveronyourLinuxmachine,youneedtocreateafilecalled
dhcpd.confinthe/etcdirectory.Thisfilecontainsalltheinformationthatthe
daemonneedswhilestartingup.Thisfileisinthefollowingformat（theline
numbersarenotpartofthefile,they'refortheexplanationthatfollows）:
subnet192.168.1.0netmask255.255.255.0{
range192.168.1.10192.168.1.250;
default-lease-time86400;
max-lease-time259200;
optionsubnet-mask255.255.255.0;
optionbroadcast-address192.168.1.255;
optionrouters192.168.1.1;
optiondomain-name-servers192.168.1.1;
optiondomain-name"";
}
Letslookattheselinesabitmoreclosely.Thefirstlinespecifiesthe（sub）
networkthattheDHCPserveristomanageormaintain.Withinthisnetwork,we
havetoconfiguredifferentparameters（writtenwithinthecurlybraces）.
ThenextlinecontainstherangefromwhichtheserverpicksupIPaddressesto
allocate.ThestartingandendingIPaddressesareenteredhere.Line3contains
thedefaultleasetime.Aleaseistheamountoftimethataparticularmachine
canholdanIPaddressbeforehavingtorenewtheleasewiththeserver.Thevalue
isgiveninnumberofseconds,so86400standsforoneday.Thenextline,
max-lease-time,specifiesthemaximumamountoftimethatamachinecanholdonto
aspecificIPaddress.
Thencomeotheroptionsthatwillalsobetransmittedtothemachine.Theseinclude
thesubnetmask,therouter,thedomainnameserver,andthedomainname.
Oncethisisdone,youneedtocreateafilecalleddhcpd.leases,alsointhe
/etc/directory,whichwillcontaininformationaboutwhichIPaddresshasbeen
allocatedtowhichmachine.Sinceallthiswillbedonebytheserver,allyouneed
todoiscreatea0bytefilewiththecommand,touch/etc/dhcpd.leases.
Thenextsteprequiresyoutoaddabroadcastroute.Dothisbyappendingtheline
/sbin/routeadd-host255.255.255.255deveth0to/etc/rc.d/rc.local.
Finally,makesureDHCPisstartedatbootup.YoucandothisbyrunningSetup,
choosingntsysv,andenablingdhcpd.Restartthemachine,bygivingthecommandsync,
followedbyreboot.
YourDHCPserverwillbeupandrunningafterthemachinestartsup.Anymachine
thatlogsonthenetworkwillreceiveanIPaddressandallotherparameters
automatically.Ifit'saWin95client,youcancheckallthesettingsbyrunning
winipcfgintheRundialogbox.
TheremaybecaseswhenyouneedtoassignaparticularmachinethesameIPaddress
always.Youcaneitherhardwiretheinformationinthecomputeroraddthefollowing
linestothedhcpd.conffile.
hostmynotebook{
hardwareethernet00:
80:
C8:
85:
B5:
D2;
fixed-address192.168.1.20;
optionhost-name"mynotebook";
}
Thisspecifiestheethernetaddress,whichwillbeunique,theIPaddressthatwillalways
beallocatedtothatmachine,andahostname.
WithDHCP,thenetworkadministrator'snightmareofcorrectlysettingupIPaddresses
onmachinessimplyvanishes.You'llneverneedtomanuallyconfigureanothermachine
everagain.
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