5.4）通过DHCP服务器租约文件查看具体租约

租约文件的路径: /var/lib/dhcpd/dhcpd.leases

[root@baism ~]# cat /var/lib/dhcpd/dhcpd.leases

# The format of this file is documented in the dhcpd.leases(5) manual page.

# This lease file was written by isc-dhcp-4.2.5

lease 192.168.11.154 {

starts 4 2019/02/21 03:41:12;

ends 4 2019/02/21 03:43:12;

tstp 4 2019/02/21 03:43:12;

cltt 4 2019/02/21 03:41:12;

binding state free;

hardware ethernet ac:87:a3:02:8d:5d;

uid "\001\254\207\243\002\215]";

client-hostname "baismdeMBP";

}

lease 192.168.11.153 {

starts 4 2019/02/21 03:54:27;

ends 4 2019/02/21 03:56:27;

tstp 4 2019/02/21 03:56:27;

cltt 4 2019/02/21 03:54:27;

binding state free;

hardware ethernet 00:0c:29:97:97:11;

uid "\001\000\014)\227\227\021";

client-hostname "cool-PC";

}

server-duid "\000\001\000\001$\000\315\373\000\014) u\271";

lease 192.168.11.155 {

starts 4 2019/02/21 13:37:42;

ends 4 2019/02/21 15:37:42;

cltt 4 2019/02/21 13:37:42;

binding state active;

next binding state free;

rewind binding state free;

hardware ethernet 00:0c:29:1a:f8:c7;

}

#发现租约

lease 192.168.11.156 {

starts 4 2019/02/21 13:40:45; 租约开始时间

ends 4 2019/02/21 15:40:45; 租约结束时间，正好是两个小时

cltt 4 2019/02/21 13:40:45;

binding state active;

next binding state free;

rewind binding state free;

hardware ethernet 00:0c:29:1a:f8:bd;

}

注意：当你发现这里的时间和你的服务器时间不一致的时候，建议你修改时区解决问题，一般是差8个小时，大家明白就好。

5.5）保留IP

在IP租约到期后，如果无法续订租约，client只能乖乖交出IP地址，重新获得一个其他IP使用。但是在公司有些服务器的IP地址是不能变化的，因为变了用户就无法连接到服务器了，比如公司文件服务器、打印服务器等等。那么在这种环境中我们既想使用DHCP管理公司IP，又想实现部分机器的IP永久不变，那么怎么实现呢。

DHCP的作者在写DHCP的时候也想到了这个问题，提出了保留IP的概念，就是将某些IP保留，然后服务器来获得IP的时候，根据其MAC地址做匹配，将对应的IP分给它即可。

教学案例:希望这个MAC地址为00:0C:29:1A:F8:C7的网卡能永久获得IP 192.168.11.252，实现方式如下:

a、在配置文件/etc/dhcp/dhcpd.conf末尾添加以下内容

host print {

hardware ethernet 00:0C:29:1A:F8:C7;

fixed-address 192.168.11.252;

}

host print host为指令，print是个名字，随便起，但是最好有意义，要不过一段你也记不住了。

hardware ethernet 指定以太网网卡MAC地址

fixed-address 指定要绑定的IP

b、重启DHCP服务

[root@baism ~]# systemctl restart dhcpd

c、测试，登陆测试机，释放挡墙IP，重新获得新的IP，查看IP地址是否正确分发

[root@bogon 桌面]# ifconfig eth1

eth1 Link encap:Ethernet HWaddr 00:0C:29:1A:F8:C7

inet addr:192.168.11.155 Bcast:192.168.11.255 Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe1a:f8c7/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:4071 errors:0 dropped:0 overruns:0 frame:0

TX packets:187 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:433880 (423.7 KiB) TX bytes:16888 (16.4 KiB)

[root@bogon 桌面]# dhclient -r eth1

[root@bogon 桌面]# dhclient -d eth1

Internet Systems Consortium DHCP Client 4.1.1-P1

For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth1/00:0c:29:1a:f8:c7

Sending on LPF/eth1/00:0c:29:1a:f8:c7

Sending on Socket/fallback

DHCPDISCOVER on eth1 to 255.255.255.255 port 67 interval 4 (xid=0x45c162c2)

DHCPOFFER from 192.168.11.16

DHCPREQUEST on eth1 to 255.255.255.255 port 67 (xid=0x45c162c2)

DHCPACK from 192.168.11.16 (xid=0x45c162c2)

bound to 192.168.11.252 -- renewal in 2881 seconds.

^C

[root@bogon 桌面]# ifconfig eth1

eth1 Link encap:Ethernet HWaddr 00:0C:29:1A:F8:C7

inet addr:192.168.11.252 Bcast:192.168.11.255 Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:fe1a:f8c7/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:4081 errors:0 dropped:0 overruns:0 frame:0

TX packets:191 errors:0 dropped:0 overruns:0 carrier:0

collisions:0 txqueuelen:1000

RX bytes:436337 (426.1 KiB) TX bytes:17656 (17.2 KiB)

完美！

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DHCP服务配置-通过DHCP服务器租约文件查看具体租约

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