IT博客汇 | DHCP：查看已经分配出去的IP地址

DHCP：查看已经分配出去的IP地址

Adamhuan发表于 2017-03-01 01:52:04

我们知道，DHCP可以动态的分配IP地址。
但是，我们怎么知道DHCP到底分配出了哪些地址？难道去网段里面去扫描？

这当然是可行的方法之一，但是，有更好的方法。

DHCPD服务，会将已经分配出去的IP的相关信息记录在一个文件里面：/var/lib/dhcpd/dhcpd.leases

具体如下：

[root@center-me ~]# 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 10.158.1.104 {
  starts 3 2017/02/15 06:43:38;
  ends 3 2017/02/15 12:43:38;
  tstp 3 2017/02/15 12:43:38;
  cltt 3 2017/02/15 06:43:38;
  binding state free;
  hardware ethernet 00:50:56:84:67:c1;
}
lease 10.158.1.103 {
  starts 3 2017/02/15 06:52:30;
  ends 3 2017/02/15 12:52:30;
  tstp 3 2017/02/15 12:52:30;
  cltt 3 2017/02/15 06:52:30;
  binding state free;
  hardware ethernet 00:50:56:84:1d:b1;
}
lease 10.158.1.105 {
  starts 3 2017/02/15 06:56:05;
  ends 3 2017/02/15 12:56:05;
  tstp 3 2017/02/15 12:56:05;
  cltt 3 2017/02/15 06:56:05;
  binding state free;
  hardware ethernet 00:50:56:84:00:8a;
}
lease 10.158.1.106 {
  starts 4 2017/02/16 03:00:06;
  ends 4 2017/02/16 09:00:06;
  tstp 4 2017/02/16 09:00:06;
  cltt 4 2017/02/16 03:00:06;
  binding state free;
  hardware ethernet 00:50:56:84:22:fa;
  set vendorclass = "PXEClient:Arch:00000:UNDI:002001";
}
lease 10.158.1.107 {
  starts 5 2017/02/17 09:26:32;
  ends 5 2017/02/17 15:26:32;
  tstp 5 2017/02/17 15:26:32;
  cltt 5 2017/02/17 09:26:32;
  binding state free;
  hardware ethernet 00:50:56:a6:0c:5b;
}
lease 10.158.1.108 {
  starts 1 2017/02/20 03:16:36;
  ends 1 2017/02/20 09:16:36;
  tstp 1 2017/02/20 09:16:36;
  cltt 1 2017/02/20 03:16:36;
  binding state free;
  hardware ethernet 00:50:56:84:62:bd;
  uid "\001\000PV\204b\275";
  set vendorclass = "MSFT 5.0";
}
lease 10.158.1.109 {
  starts 1 2017/02/20 05:50:30;
  ends 1 2017/02/20 11:50:30;
  tstp 1 2017/02/20 11:50:30;
  cltt 1 2017/02/20 05:50:30;
  binding state free;
  hardware ethernet 00:50:56:84:71:71;
  set vendorclass = "PXEClient:Arch:00000:UNDI:002001";
}
lease 10.158.1.117 {
  starts 5 2017/02/24 05:21:50;
  ends 5 2017/02/24 11:21:50;
  tstp 5 2017/02/24 11:21:50;
  cltt 5 2017/02/24 05:21:50;
  binding state free;
  hardware ethernet 00:50:56:84:00:c8;
}
lease 10.158.1.121 {
  starts 5 2017/02/24 05:41:18;
  ends 5 2017/02/24 11:41:18;
  tstp 5 2017/02/24 11:41:18;
  cltt 5 2017/02/24 05:41:18;
  binding state free;
  hardware ethernet 00:50:56:84:01:8e;
}
lease 10.158.1.116 {
  starts 5 2017/02/24 05:57:48;
  ends 5 2017/02/24 11:57:48;
  tstp 5 2017/02/24 11:57:48;
  cltt 5 2017/02/24 05:57:48;
  binding state free;
  hardware ethernet 00:50:56:84:2b:e2;
}
lease 10.158.1.119 {
  starts 5 2017/02/24 06:02:21;
  ends 5 2017/02/24 12:02:21;
  tstp 5 2017/02/24 12:02:21;
  cltt 5 2017/02/24 06:02:21;
  binding state free;
  hardware ethernet 00:50:56:84:5a:79;
}
lease 10.158.1.122 {
  starts 5 2017/02/24 06:10:04;
  ends 5 2017/02/24 12:10:04;
  tstp 5 2017/02/24 12:10:04;
  cltt 5 2017/02/24 06:10:04;
  binding state free;
  hardware ethernet 00:50:56:84:60:d9;
}
lease 10.158.1.101 {
  starts 2 2017/02/28 20:16:33;
  ends 3 2017/03/01 02:16:33;
  cltt 2 2017/02/28 20:16:33;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 00:50:56:84:6a:7d;
  uid "\001\000PV\204j}";
  set vendorclass = "udhcp 1.23.1";
  client-hostname "boot2docker";
}
lease 10.158.1.102 {
  starts 2 2017/02/28 23:15:25;
  ends 3 2017/03/01 05:15:25;
  cltt 2 2017/02/28 23:15:25;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 00:50:56:02:01:00;
  uid "\001\000PV\002\001\000";
  set vendorclass = "MSFT 5.0";
  client-hostname "WIN-PVEA1SONOMA";
}
server-duid "\000\001\000\001 6\240\236\000PV\204\013`";

lease 10.158.1.101 {
  starts 2 2017/02/28 23:16:33;
  ends 3 2017/03/01 05:16:33;
  cltt 2 2017/02/28 23:16:33;
  binding state active;
  next binding state free;
  rewind binding state free;
  hardware ethernet 00:50:56:84:6a:7d;
  uid "\001\000PV\204j}";
  set vendorclass = "udhcp 1.23.1";
  client-hostname "boot2docker";
}
[root@center-me ~]# 
[root@center-me ~]#

可以看到，改文件中可能会有重复的记录条目。
更清楚的看到，如下：

[root@center-me ~]# cat /var/lib/dhcpd/dhcpd.leases | grep lease | cut -d' ' -f2 | grep -v -E "The|This"
10.158.1.104
10.158.1.103
10.158.1.105
10.158.1.106
10.158.1.107
10.158.1.108
10.158.1.109
10.158.1.117
10.158.1.121
10.158.1.116
10.158.1.119
10.158.1.122
10.158.1.101
10.158.1.102
10.158.1.101
[root@center-me ~]#

可以看到【101】是重复的。

要想筛选出来不重复的IP列表可以通过脚本或者一句命令实现：

[root@center-me ~]# cat /var/lib/dhcpd/dhcpd.leases | grep lease | cut -d' ' -f2 | grep -v -E "The|This" | sort -u
10.158.1.101
10.158.1.102
10.158.1.103
10.158.1.104
10.158.1.105
10.158.1.106
10.158.1.107
10.158.1.108
10.158.1.109
10.158.1.116
10.158.1.117
10.158.1.119
10.158.1.121
10.158.1.122
[root@center-me ~]#

————————————
Done。