第十六章、DHCP 服务器

[root@linux ~]# vi /etc/dhcpd.conf
# 1. 整体的环境设置
#    当底下的 subnet 与 host 没有设置时，以这里的设置值为准喔！
ddns-update-style               none;          <==不要更新 DDNS 的设置
default-lease-time              259200;        <==缺省租约为 3 天
max-lease-time                  518400;        <==最大租约为 6 天
option routers                  192.168.1.254; <==这就是缺省路由
option broadcast-address        192.168.1.255; <==这是广播地址啊
option domain-name-servers      168.95.1.1, 139.175.10.20;
# 上面是 DNS 的 IP 设置，这个设置值会修改用户端的 /etc/resolv.conf 文件内容！
# 此外，你可以设置多部 DNS 主机，不过必须要以逗号『 , 』分隔开才行。

# 2. 关于动态分配的 IP
#     Network_IP↓        Netmask_IP↓
subnet 192.168.1.0 netmask 255.255.255.0 {
    range 192.168.1.21 192.168.1.100;      <==分配的 IP 范围
    option subnet-mask   255.255.255.0; <==可重复设置 netmask 地址
    option nis-domain    "vbird.tsai";  <==额外给的 NIS 相关参数
    option domain-name   "vbird.tsai";  <==在 /etc/resolv.conf 给一个搜索领域

    # 3. 关于静态的 IP 啊！
    #    主机名称↓
    host vbird-inside {
        hardware ethernet    00:40:95:30:43:B4; <==用户端网卡 MAC
        fixed-address        192.168.1.5;       <==给予固定的 IP
    }
}
# 相关的设置参数意义，请查找前一小节的介绍，或者 man dhcpd.conf

[root@linux ~]# vi /etc/sysconfig/dhcpd
DHCPDARGS="eth0"

[root@linux ~]# vi /etc/init.d/dhcpd
# 约在第 58 行左右会找到：
        daemon /usr/sbin/dhcpd ${DHCPDARGS} 2>/dev/null 

1. 就启动吧！
[root@linux ~]# /etc/init.d/dhcpd start

2. 看看端口口启动的情况
[root@linux ~]# netstat -tlunp
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address PID/Program name
udp        0      0 0.0.0.0:67    0.0.0.0:*       7294/dhcpd

3. 看看注册表的输出信息
[root@linux ~]# tail -n 30 /var/log/messages
Dec 5 10:58 linux dhcpd: Internet Systems Consortium DHCP Server V3.0.1
Dec 5 10:58 linux dhcpd: Copyright 2004 Internet Systems Consortium.
Dec 5 10:58 linux dhcpd: All rights reserved.
Dec 5 10:58 linux dhcpd: For info, please visit http://www.isc.org/sw/dhcp/
Dec 5 10:58 linux dhcpd: Wrote 0 deleted host decls to leases file.
Dec 5 10:58 linux dhcpd: Wrote 0 new dynamic host decls to leases file.
Dec 5 10:58 linux dhcpd: Wrote 0 leases to leases file.
Dec 5 10:58 linux dhcpd: Listening on LPF/eth0/00:40:fa:25:2a:db/192.168.1/24
Dec 5 10:58 linux dhcpd: dhcpd startup succeeded

Dec 5 11:11 linux dhcpd: /etc/dhcpd.conf line 10: semicolon expected.
Dec 5 11:11 linux dhcpd: subnet
Dec 5 11:11 linux dhcpd: ^
Dec 5 11:11 linux dhcpd: Configuration file errors encountered -- exiting

** You must add a ddns-update-style statement to /etc/dhcpd.conf.
   To get the same behaviour as in 3.0b2pl11 and previous
   versions, add a line that says "ddns-update-style ad-hoc;"
   Please read the dhcpd.conf manual page for more information. **

[root@linux ~]# vi /etc/hosts
127.0.0.1　　 localhost.localdomain localhost
192.168.1.254  vbird-server
192.168.1.5　  static-ip
192.168.1.21 　dynamic-021
192.168.1.22 　dynamic-022
.....
192.168.1.100  dynamic-100

[root@client ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=dhcp  <==就是他！指定这一个就对了！
ONBOOT=yes

[root@client ~]# /etc/init.d/network restart

1. DNS 的 IP 会被更动呢！查阅一下 resolv.conf 先：
[root@linux ~]# cat /etc/resolv.conf
; generated by /sbin/dhclient-script
search vbird.tsai          <==是否记得设置过 domain-name 呢？
nameserver 168.95.1.1      <==这就是我们原本的设置值。
nameserver 139.175.10.20

2. 观察一下路由啦！
[root@linux ~]# route -n
Kernel IP routing table
Destination     Gateway        Genmask        Flags  Iface
192.168.1.0     0.0.0.0        255.255.255.0  U      eth0
169.254.0.0     0.0.0.0        255.255.0.0    U      eth0
0.0.0.0         192.168.1.254  0.0.0.0        UG     eth0
# 嗯！没错！路由也被正确的捉到了！OK的啦！

3. 察看一下用户端的指令吧！
[root@linux ~]# netstat -tlunp
Proto Recv-Q Send-Q Local Address  Foreign Address State  PID/Program name
udp        0      0 0.0.0.0:68     0.0.0.0:*              3996/dhclient
# 你没看错！确实是有个小程序在监测 DHCP 的连接状态呐！

4. 看一看用户端租约所记载的信息吧！
[root@linux ~]# cat /var/lib/dhcp/dhclient-eth0.leases
lease {
  interface "eth0";
  fixed-address 192.168.1.100;  <==这就是为啥我每次取得的 IP 是固定的。
  option subnet-mask 255.255.255.0;
  option routers 192.168.1.254;
  option dhcp-lease-time 259200;
  option dhcp-message-type 5;
  option domain-name-servers 168.95.1.1,139.175.10.20;
  option dhcp-server-identifier 192.168.1.254;
  option nis-domain "vbird.tsai";
  option broadcast-address 192.168.1.255;
  option domain-name "vbird.tsai";
  renew 3 2006/12/6 18:15:41;   <==下一次预计更新 (renew) 的时间点
  rebind 5 2006/12/8 05:26:26;
  expire 5 2006/12/8 14:26:26;
}
# 这个文件会记录该适配器所曾经要求过的 DHCP 信息喔！重要！
# 有没有看出来，他几乎就与你设置的 /etc/dhcpd.conf 类似？ ^_^

5. 额外看一下 NIS 的领域名称有没有设置妥当啊？
[root@linux ~]# nisdomainname
vbird.tsai   <==因为我们有设置 nis-domain 的项目啊！

[root@linux ~]# cat /var/lib/dhcp/dhcpd.leases
lease 192.168.1.99 {  <==就是那部 Windows 的纪录
  starts 2 2006/12/05 14:23:37;
  ends 5 2006/12/08 14:23:37;
  binding state active;
  next binding state free;
  hardware ethernet 00-d0-18-af-6e-81;
  uid "\001\000\340\030\257n\003";
  client-hostname "vbird_work";
}
lease 192.168.1.100 { <==就是那部 Linux 的纪录
  starts 2 2006/12/05 15:37:33;
  ends 5 2006/12/08 15:37:33;
  binding state active;
  next binding state free;
  hardware ethernet 00:30:20:1d:c3:6e;
}

[root@linux ~]# gcc -O -Wall -o ether-wake ether-wake.c

[root@linux ~]# ./ether-wake 11:22:33:44:55:66

# 更多功能可以这样查阅喔：
[root@linux ~]# ./ether-wake -u