DHCP服务搭建

Posted 2021-01-10

DHCP实验

实验规划及环境准备
1、DHCP服务器应该配置成一个静态IP（最好使用仅主机模式做实验）
2、VMware内置DHCP服务器，应禁止仅主机模式VMnet1的DHCP服务
3、关闭selinux和防火墙
实验器材准备
2台虚拟机（CentOS7、CentOS7C）。7作为客户机（IP为192.168.137.200），7C作为客户机
.

1、为CentOS7主机添加一块仅主机网卡，并配置成静态IP=192.168.137.200（这个主机还有一块桥接网卡）

bash# vim /etc/sysconfig/network-scripts/ifcfg-ens33
TYPE="Ethernet"
BOOTPROTO="none"
NAME="ens33"
UUID="af78583d-e2d9-42ba-83f1-42659c869aed"
DEVICE="ens33"
ONBOOT="yes"
IPADDR="192.168.137.200"
NETMASK="255.255.255.0"

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2、将CentOS7C主机添加一块仅主机网卡，并配置成通过dhcp服务获得IP地址

bash# vim /etc/sysconfig/network-scripts/ifcfg-ens33
TYPE="Ethernet"
BOOTPROTO="dhcp"
NAME="ens33"
DEVICE="ens33"
ONBOOT="yes"

.
3、重启CentOS7C之后可以发现，主机CentOS7C的网卡上是没有IP地址的

bash# ifconfig 

.
4、开始在CentOS7主机上配置DHCP服务
①、在CentOS7上安装dhcp包，并尝试启动dhcp服务

bash# yum install -y dhcp
bash# systemctl start dhcpd    //发现启动不了，原因是主配置文件无内容

②、查看主配置文件之后，发现是空的，文件中提示有配置模板文件/usr/share/doc/dhcp-4.2.5/dhcpd.conf.example，复制该文件至/etc/dhcp/dhcpd.conf，添加子网和地址池

bash# cp /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf
bash# vim /etc/dhcp/dhcpd.conf
# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "example.org";        //从DHCP服务器获取的域后缀，/etc/resolv.conf中的search，用于补全后缀
option domain-name-servers 114.114.114.114,1.1.1.1    //指明DNS服务器。放在此处所有子网有效

default-lease-time 600; //默认租期600s。租期未到，即使机器关机，IP地址也会被占用，租期过长，主机过多，新主机可能拿不到地址
max-lease-time 7200;    //最长租期，客户端可以向服务器申请租期时间，这个是客户端可以申请的最大租期时间

log-facility local7;

subnet 192.168.137.0 netmask 255.255.255.0 {     //subnet子网声明，说明将来要为哪个子网分配地址
  range 192.168.137.100 192.168.137.199;         //地址池为192.168.137.100到192.168.137.199 
  option routers 192.168.137.1;                   //为客户端分配网关
  option domain-name-servers 114.114.114.114,1.1.1.1    //指明DNS服务器，子网中定义的优先级更高
  next-server 192.168.137.199    //指定tftp服务器，DHCP客户机可以向此主机获取引导文件
  filename "pxelinux.0";    //tftp服务器上引导文件的名字,next-server和filename用于实现自动安装
}

subnet 10.254.239.0 netmask 255.255.255.224 {
  range 10.254.239.10 10.254.239.20;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

subnet 10.254.239.32 netmask 255.255.255.224 {
  range 10.254.239.10 10.254.239.20;
  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

subnet 10.254.239.32 netmask 255.255.255.224 {
  range dynamic-bootp 10.254.239.40 10.254.239.60;
  option broadcast-address 10.254.239.31;
  option routers rtr-239-32-1.example.org;
}

subnet 10.5.5.0 netmask 255.255.255.224 {
  range 10.5.5.26 10.5.5.30;
  option domain-name-servers ns1.internal.example.org;
  option domain-name "internal.example.org";
  option routers 10.5.5.1;
  option broadcast-address 10.5.5.31;
  default-lease-time 600;
  max-lease-time 7200;
}

host passacaglia {
  hardware ethernet 0:0:c0:5d:bd:95;
  filename "vmunix.passacaglia";
  server-name "toccata.fugue.com";
}

# 以下操作可以做MAC绑定固定IP
host fantasia {
  #hardware ethernet 00:0c:29:f4:0a:fd;    //客户机网卡的MAC地址，可以做静态地址绑定
  #fixed-address 192.168.30.100;    //为此MAC地址分配的固定IP，也可以在此处配置网关DNS等信息
  #option routers 192.168.137.1    //为客户机指定网关
  #option domain-name-servers 223.5.5.5；  //为客户机指定阿里的DNS服务器
}

class "foo" {
  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

shared-network 224-29 {
  subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
  }
  subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
  }
  pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
  }
  pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
  }
}

③、CentOS7启动dhcpd服务

bash# systemctl start dhcpd.service

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5、查看CentOS7C是否获得IP地址

bash# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.137.129  netmask 255.255.255.0  broadcast 192.168.137.255
        inet6 fe80::777d:b963:b4c7:8408  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:f4:0a:fd  txqueuelen 1000  (Ethernet)
        RX packets 726  bytes 191927 (187.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 374  bytes 67729 (66.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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6、查看CentOS7中的租约信息文件/var/lib/dhcpd/dhcpd.leases

bash# vim /var/lib/dhcpd/dhcpd.leases
lease 192.168.137.129 {
  starts 5 2018/10/05 14:55:30;    //租约开始时间，UTC时间，比北京时间早8个小时
  ends 5 2018/10/05 15:05:30;      //租约结束时间，和开始时间正好差600s
  cltt 5 2018/10/05 14:55:30;      
  binding state active;            
  next binding state free;
  rewind binding state free;
  hardware ethernet 00:0c:29:f4:0a:fd;
  client-hostname "VCentOS75";
}

.
7、查看客户端租约文件

bash# dhclient -d
bash# vim /var/lib/dhclient/dhclient.leases
lease {
  interface "eth0";
  fixed-address 192.168.137.129;   //确实获得了地址池中的地址
  option subnet-mask 255.255.255.0;
  option routers 192.168.137.1;
  option dhcp-lease-time 600;
  option dhcp-message-type 5;
  option domain-name-servers 114.114.114.114,1.1.1.1;
  option dhcp-server-identifier 192.168.137.200;  //从DHCP服务器192.168.137.200上获取的IP地址
  option domain-name "example.org";
  renew 5 2018/10/05 15:14:47;
  rebind 5 2018/10/05 15:19:45;
  expire 5 2018/10/05 15:21:00;
}