DHCP原理与自建DHCP服务

#安装dhcp服务
[root@study1 ~]# yum install dhcp
[root@study1 ~]# rpm -ql dhcp
/etc/NetworkManager
/etc/NetworkManager/dispatcher.d
/etc/NetworkManager/dispatcher.d/12-dhcpd
/etc/dhcp/dhcpd.conf
/etc/dhcp/dhcpd6.conf
/etc/dhcp/scripts
/etc/dhcp/scripts/README.scripts
/etc/openldap/schema/dhcp.schema
/etc/sysconfig/dhcpd
/usr/bin/omshell
/usr/lib/systemd/system/dhcpd.service
/usr/lib/systemd/system/dhcpd6.service
/usr/lib/systemd/system/dhcrelay.service
/usr/sbin/dhcpd
/usr/sbin/dhcrelay
/usr/share/doc/dhcp-4.2.5
/usr/share/doc/dhcp-4.2.5/dhcpd.conf.example
/usr/share/doc/dhcp-4.2.5/dhcpd6.conf.example
/usr/share/doc/dhcp-4.2.5/ldap
/usr/share/doc/dhcp-4.2.5/ldap/README.ldap
/usr/share/doc/dhcp-4.2.5/ldap/dhcp.schema
/usr/share/doc/dhcp-4.2.5/ldap/dhcpd-conf-to-ldap
/usr/share/man/man1/omshell.1.gz
/usr/share/man/man5/dhcpd.conf.5.gz
/usr/share/man/man5/dhcpd.leases.5.gz
/usr/share/man/man8/dhcpd.8.gz
/usr/share/man/man8/dhcrelay.8.gz
/usr/share/systemtap/tapset/dhcpd.stp
/var/lib/dhcpd
/var/lib/dhcpd/dhcpd.leases
/var/lib/dhcpd/dhcpd6.leases


#复制配置模板修改
[root@study1 ~]# cp /usr/share/doc/dhcp-4.2.5/dhcpd.conf.example /etc/dhcp/dhcpd.conf


#修改dhcp配置
[root@study1 ~]# vim /etc/dhcp/dhcpd.conf
option domain-name "t.com"; //DNS域名
option domain-name-servers dns.t.com, ns1.t.com;  //DNS的域服务器

default-lease-time 600; /默认的租约时间，秒为单位
max-lease-time 7200;  //最大的租约时间，秒为单位

log-facility local7; //定义日志服务，可以在日志配置文件中查看具体日志位置，默认是：/var/log/boog.log，但是在/var/log/messages里面也会记录dhcp日志

subnet 10.10.2.0 netmask 255.255.255.0 { //--分配的网段及子网掩码，代表只在10.10.2.0这个C类网段里生效，子网掩码设为255.255.255.0

        range   10.10.2.10 10.10.2.20; //地址池：代表给客户机分配可用的IP范围，起始到结束,尽量不要包含DHCP服务器的IP地址
        option routers 10.10.2.1; //指配置分配给客户机的路由网关，这里我们设为DHCP服务器的IP地址
        option  domain-name-servers 10.10.2.1, dns.t.com;  //配置要分配给客户端的DNS地址，这里我们设为DHCP服务器的IP地址
}

#启动服务
[root@study1 ~]# systemctl start dhcpd.service
[root@study1 ~]# systemctl status dhcpd
● dhcpd.service - DHCPv4 Server Daemon
   Loaded: loaded (/usr/lib/systemd/system/dhcpd.service; disabled; vendor preset: disabled)
   Active: active (running) since 四 2020-02-27 20:00:29 CST; 23s ago
     Docs: man:dhcpd(8)
           man:dhcpd.conf(5)
 Main PID: 2973 (dhcpd)
   Status: "Dispatching packets..."
   CGroup: /system.slice/dhcpd.service
           └─2973 /usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid

## 客户机测试
# 测试使用虚拟机的仅主机模式 去掉DHCP
[root@study02 ~]# dhclient -d
Internet Systems Consortium DHCP Client 4.2.5
Copyright 2004-2013 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on    LPF/eth0/00:0c:29:7c:68:4e
Sending on      LPF/eth8/00:0c:29:7c:68:4e
Sending on      Socket/fal Iback 
DHCPD ISCOVER on et.h0 to 255 .255.255.255 port 67 interval 6 (xid =0x78318b9a )
DHCPREQUEST on et.h0 to 255.255.255.255 port 67 (xid=8x78318b9a)
DHCPOFFER from 10.10.2.1
DHCPACK from 10.10.2.1 (xid=0x78318b9a )
bound to 10.10.2.10 -- renewal in 235 seconds .

[root@study01 ~]# cat /var/1ib/dhcpd/dhcpd.leases
lease 10.10.2.10 {
starts 4 2020/02/27 12:34:05:
ends 4 2020/02/27 12:44:05:
cltt 4 2020/02/27 12:34:05:
binding state act ive;
next binding state free:
rewind binding state free;
hardware ethernet 00:0c:29:7c:68:4e;
client-hostname 'node2" ;
}