dhcp服务器在企业网中的应用

 

DHCP简介
 DHCP(Dynamic Host Configuration Protocol,动态主机配置协议)是一种基于客户/服务器模式的服务协议。工做原理其实很简单,就是在安装有DHCP服务器的两种网络中,客户端启动时自动与DHCP服务器通讯,要求服务器提供自动分配ip地址的服务,而安装了DHCP服务软件的服务器响应这个要求。并向客户端发送出合法的IP地址。
DHCP工做流程

 

 

DHCP ip地址租约
1.       限定租期
2.       永久租用
DHCP 租约的更新
1. 开机在关机后ip地址更新
2. 租期到50%后发送dhcp请求更新地址租约
3. 若是更新未成功到租期的87.5%是在发送dhcp请求更新租约
4. 若是以上两次都未成功租约到期后从新更新租约
DHCP安装前的准备工做
1. 经过命令确认系统中是否已经安装DHCP服务
    [root@localhost ~]# rpm -qa |grep dhcp
dhcp-3.0.5-21.el5
dhcpv6-client-1.0.10-17.el5
2. 配置dhcrelay守护进程
   若是dhcp服务器须要用于远程网络,那么必须把dhcrelay守护进程配置在局域网之间的路由器/网关计算机上。
3.       把dhcp服务器的ip地址设置成为静态ip地址

 

 

 

案例一(dhcp单区域)
1.挂在光盘
[root@localhost ~]#mkdir /mnt/cdrom        建立一个用户挂载的光盘目录
[root@localhost ~]#mount /dev/cdrom /mnt/cdrom 挂在光盘
2. 安装dhcp服务
[root@localhost ~]#cd /mnt/cdrom       
[root@localhost ~]#prm –ivh dhcp-3.0.5-13.e15.i386.rpm 安装dhcp服务的命令
3.配置dhcp服务器的配置文件
[root@localhost ~]# vim /etc/dhcpd.conf      进入配置目录
1 #
 2 ddns-update-style interim; #配置使用过分性DHCP-DNS互动模式。
 3 ignore client-updates;       #忽略客户端更新
 4
 5 subnet 192.168.1.0 netmask 255.255.255.0 { 网段声明
 6
 7 # --- default gateway
 8          option routers                  192.168.1.254; 定义网关
 9          option subnet-mask              255.255.255.0; 定义子网掩码
 10
 11          option nis-domain               "domain.org"; 设置nis域名
 12          option domain-name              "domain.org"; 设置域名
 13       option domain-name-servers      222.88.88.88; (这里是电信的dns)
 14
 15          option time-offset              -18000; # 设置时间偏移
 16 #        option ntp-servers              192.168.1.1; 设置ntp服务器
 17 #        option netbios-name-servers     192.168.1.1;
  18 # --- Selects point-to-point node (default is hybrid). Don't change this unless
 19 # -- you understand Netbios very well
  20 #       option netbios-node-type 2;    设置nis服务的节点(不建议修改)
 21
 22          range dynamic-bootp 192.168.0.128 192.168.0.254; 设置地址池
 23          default-lease-time 21600;                        设置默认租期
 24          max-lease-time 43200;                           设置最大租期
 25
 26          # we want the nameserver to appear at a fixed address
 27          host ns {
 28                  next-server marvin.redhat.com;
 29                  hardware ethernet 12:34:56:78:AB:CD;
 30                  fixed-address 207.175.42.254;
 31          }
 32 }
 3 3 # DHCP Server Configuration file.
 34 #    see /usr/share/doc/dhcp*/dhcpd.conf.sample 
 35 #
4.利用一个客户机测试的结果

 

 

 

 

案例二(dhcp超级做用域)
咱们知道一个C类的地址能为254台PC提供ip地址上网用,若是一个公司的电脑数量多于254台这是用一个C类的地址就不够用了。对于这种状况有两种解决方案一种是用一个B类的地址,第二种是创建一个由C类地址主城的超级做用域。
1.       第一步   跟案例一同样
2.       第二部 跟案例一同样
3.配置dhcp服务器的配置文件
[root@localhost ~]# vim /etc/dhcpd.conf      进入配置目录
5 shared-network zzdx {       配置的超级做用域zzdx是超级做用域的名称
 6 subnet 192.168.1.0 netmask 255.255.255.0 {
 7
 8 # --- default gateway
 9          option routers                  192.168.1.254;
 10          option subnet-mask              255.255.255.0;
 11
 12          option nis-domain               "domain.org";
 13          option domain-name              "abc.com";
 14          option domain-name-servers      222.88.88.88;
 15
 16          option time-offset              -18000; # Eastern Standard Time
 17 #        option ntp-servers              192.168.1.1;
 18 #        option netbios-name-servers     192.168.1.1;
 19 # --- Selects point-to-point node (default is hybrid). Don't change this unless
 20 # -- you understand Netbios very well
 21 #        option netbios-node-type 2;
 22
 23          range dynamic-bootp 192.168.1.2 192.168.1.253;
 24          default-lease-time 21600;
 25          max-lease-time 43200;
 26
 27          # we want the nameserver to appear at a fixed address
 28          host ns {
 29                  next-server marvin.redhat.com;
 30                  hardware ethernet 12:34:56:78:AB:CD;
 31                  fixed-address 207.175.42.254;
 32          }
 33 }
 34 subnet 192.168.2.0 netmask 255.255.255.0 {     配置第二个ip池
 35          option routers                  192.168.2.254;
 36          option subnet-mask              255.255.255.0;
 37          option domain-name-servers      222.88.88.88;
 38          range dynamic-bootp 192.168.2.2 192.168.2.253;
 39          default-lease-time 21600;
 40          max-lease-time 43200;
4 测试因为超级做用域的ip取值是先从一个做用域内取值知道一个做用域内的ip地址用完后才开始从第二个ip地址池内取地址。测试时能够把超级做用域中的两个地址池都改成一个ip地址。
案例三(dhcp中继)
案例拓补图

 

 

 

 

第一步 跟案例一同样
第二步 跟案例二同样
第三步 .配置dhcp服务器的配置文件
[root@localhost ~]# vim /etc/dhcpd.conf      进入配置目录
subnet 192.168.3.0 netmask 255.255.255.0 {   vlan30 的地址池
 
# --- default gateway
        option routers                  192.168.3.254;
        option subnet-mask              255.255.255.0;
 
        option domain-name              "jisu.com";
        option domain-name-servers      222.88.88.88;
 
        option time-offset              -18000; # Eastern Standard Time
        default-lease-time 21600;
        max-lease-time 43200;
 
        host ns {
                next-server marvin.redhat.com;
                hardware ethernet 12:34:56:78:AB:CD;
                fixed-address 207.175.42.254;
        }
}
subnet 192.168.2.0 netmask 255.255.255.0 {     vlan20 的地址池
 
# --- default gateway
        option routers                  192.168.2.254;
        option subnet-mask              255.255.255.0;
 
        option domain-name              "caiwu.com";
        option domain-name-servers      222.88.88.88;
 
        option time-offset              -18000; # Eastern Standard Time
        default-lease-time 21600;
        max-lease-time 43200;
        host www {
                next-server marvin.redhat.com;
                hardware ethernet 12:34:56:78:AB:CD;
                fixed-address 207.175.42.254;
        }
}
subnet 192.168.1.0 netmask 255.255.255.0 {    服务器集群的地址池
}
配置dhcp中继服务器
网卡配置
eth0       Link encap:Ethernet HWaddr 00:0C:29:86:4E:97 
          inet addr:192.168.1.254 Bcast:192.168.1.255 Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe86:4e97/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:288 errors:0 dropped:0 overruns:0 frame:0
          TX packets:180 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:67880 (66.2 KiB) TX bytes:38315 (37.4 KiB)
          Interrupt:67 Base address:0x2000
 
eth1       Link encap:Ethernet HWaddr 00:0C:29:86:4E:A1 
          inet addr:192.168.2.254 Bcast:192.168.2.255 Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe86:4ea1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:232 errors:0 dropped:0 overruns:0 frame:0
          TX packets:145 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:48752 (47.6 KiB) TX bytes:31455 (30.7 KiB)
          Interrupt:67 Base address:0x2080
 
eth2       Link encap:Ethernet HWaddr 00:0C:29:86:4E:AB 
          inet addr:192.168.3.254 Bcast:192.168.3.255 Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe86:4eab/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500 Metric:1
          RX packets:128 errors:0 dropped:0 overruns:0 frame:0
          TX packets:144 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:73164 (71.4 KiB) TX bytes:31871 (31.1 KiB)
          Interrupt:75 Base address:0x2400
中继服务器的路由表
root@localhost ~]# route -n
Kernel IP routing table
Destination      Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.3.0      0.0.0.0         255.255.255.0   U     0      0        0 eth2
192.168.2.0      0.0.0.0         255.255.255.0   U     0      0        0 eth1
192.168.1.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.0.0      0.0.0.0         255.255.0.0     U     0      0        0 eth2
打开路由功能
[root@localhost ~]# vim /etc/sysctl.conf
7 net.ipv4.ip_forward = 1
 8
 9 # Controls source route verification
 10 net.ipv4.conf.de
[root@localhost ~]# sysctl –p   配置完后打卡路由功能的命令
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 4294967295
kernel.shmall = 268435456
配置dhcp中继服务
[root@localhost ~]# vim /etc/sysconfig/dhcrelay   dhcp中继的配置文件
# Command line options here
INTERFACES="eth0 eth1 eth2"
DHCPSERVERS="192.168.1.100"
开启dhcp中继服务
[root@localhost ~]# service dhcrelay start
Starting dhcrelay:                                          [ OK ]
 

 

 

 

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