(1/4): dhclient-4.1.1-53.P1.el6.centos.x86_64.rpm                       | 322 kB     00:00  

###  DHCP (Dynamic Host Configuration Protocol) is a protocol which allows
individual devices on an IP network to get their own network
configuration information (IP address, subnetmask, broadcast address,
etc.) from a DHCP server. The overall purpose of DHCP is to make it
easier to administer a large network.  The dhcp package includes the
ISC DHCP service and relay agent.


在ISC DHCP中继代理和服务。
(2/4): dhcp-4.1.1-53.P1.el6.centos.x86_64.rpm                           | 823 kB     00:00    

###DHCP (Dynamic Host Configuration Protocol) is a protocol which allows
individual devices on an IP network to get their own network
configuration information (IP address, subnetmask, broadcast address,
etc.) from a DHCP server. The overall purpose of DHCP is to make it
easier to administer a large network.  The dhcp package includes the
ISC DHCP service and relay agent.

To use DHCP on your network, install a DHCP service (or relay agent),
and on clients run a DHCP client daemon.  The dhcp package provides
the ISC DHCP service and relay agent.
(3/4): dhcp-common-4.1.1-53.P1.el6.centos.x86_64.rpm                    | 144 kB     00:00 

    ###管理包DHCP (Dynamic Host Configuration Protocol) is a protocol which allows
individual devices on an IP network to get their own network
configuration information (IP address, subnetmask, broadcast address,
etc.) from a DHCP server. The overall purpose of DHCP is to make it
easier to administer a large network.
(4/4): dhcp-devel-4.1.1-53.P1.el6.centos.x86_64.rpm                     | 158 kB     00:00    
##Header files and API documentation for using the ISC DHCP libraries.  The
libdhcpctl and libomapi static libraries are also included in this package.

 cat /etc/dhcp/dhcpd.conf

#
# DHCP Server Configuration file.
#   see /usr/share/doc/dhcp*/dhcpd.conf.sample
#   see ‘man 5 dhcpd.conf‘
#
cat /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample  > /etc/dhcp/dhcpd.conf

[root@dhcp dhcp]# cat /etc/dhcp/dhcpd.conf 
ddns-update-style interim;
ignore client-updates;

subnet 192.168.1.0 netmask 255.255.255.0 {

# --- default gateway
option routers                  192.168.1.0;
option subnet-mask              255.255.255.0;
option time-offset              -18000; # Eastern Standard Time
#       option ntp-servers              192.168.1.1;
#       option netbios-name-servers     192.168.1.1;
# --- Selects point-to-point node (default is hybrid). Don‘t change # -- you understand Netbios very well                        
#      option netbios-node-type 2;

range dynamic-bootp 192.168.1.200 192.168.1.230;
default-lease-time 21600;
max-lease-time 43200;

# we want the nameserver to appear at a fixed address
 }

dhcpd.conf参数说明

/etc/dhcpd.conf通常包括三部分：parameters、declarations 、option。

1.DHCP配置文件中的parameters（参数）：表明如何执行任务，是否要执行任务，或将哪些网络配置选项发送给客户


ddns-update-style               配置DHCP-DNS 互动更新模式。 
default-lease-time              指定确省租赁时间的长度，单位是秒。 
max-lease-time                  指定最大租赁时间长度，单位是秒。 
hardware                        指定网卡接口类型和MAC地址。 
server-name                     通知DHCP客户服务器名称。 
get-lease-hostnames flag        检查客户端使用的IP地址。 
fixed-address ip                分配给客户端一个固定的地址。 
authritative                    拒绝不正确的IP地址的要求。

2.DHCP配置文件中的declarations （声明）：用来描述网络布局、提供客户的IP地址等


shared-network                              用来告知是否一些子网络分享相同网络。 
subnet                                      描述一个IP地址是否属于该子网。 
range                                       起始IP 终止IP 提供动态分配IP 的范围。 
host                                        主机名称 参考特别的主机。 
group                                       为一组参数提供声明。 
allow unknown-clients;deny unknown-client   是否动态分配IP给未知的使用者。 
allow bootp;deny bootp                      是否响应激活查询。 
allow booting;deny booting                  是否响应使用者查询。 
filename                                    开始启动文件的名称. 应用于无盘工作站。 
next-server                                设置服务器从引导文件中装如主机名，应用于无盘工作站。

3. DHCP配置文件中的option（选项）：用来配置DHCP可选参数，全部用option关键字作为开始

subnet-mask           为客户端设定子网掩码。 
domain-name           为客户端指明DNS名字。 
domain-name-servers   为客户端指明DNS服务器IP地址。 
host-name             为客户端指定主机名称。 
routers               为客户端设定默认网关。 
broadcast-address     为客户端设定广播地址。 
ntp-server            为客户端设定网络时间服务器IP地址。 
time－offset          为客户端设定和格林威治时间的偏移时间，单位是秒。

注意：如果客户端使用的是视窗操作系统，不要选择"host-name"选项，即不要为其指定主机名称

首次获取
May 29 12:27:38 66 dhclient[26828]: DHCPDISCOVER on eth2 to 255.255.255.255 port 67 interval 8 (xid=0x3acc5b99)
May 29 12:27:38 66 dhclient[26828]: DHCPOFFER from 192.168.1.2
May 29 12:27:38 66 dhclient[26828]: DHCPREQUEST on eth2 to 255.255.255.255 port 67 (xid=0x3acc5b99)
May 29 12:27:38 66 dhclient[26828]: DHCPACK from 192.168.1.2 (xid=0x3acc5b99)
May 29 12:27:40 66 NET[26875]: /sbin/dhclient-script : updated /etc/resolv.conf
May 29 12:27:40 66 dhclient[26828]: bound to 192.168.1.47 -- renewal in 39792 seconds.

断开后重新获取
May 29 13:26:40 66 dhclient[41297]: DHCPREQUEST on eth3 to 255.255.255.255 port 67 (xid=0x207c094c)
May 29 13:26:40 66 dhclient[41297]: DHCPACK from 192.168.1.2 (xid=0x207c094c)
May 29 13:26:42 66 NET[41351]: /sbin/dhclient-script : updated /etc/resolv.conf
May 29 13:26:42 66 dhclient[41297]: bound to 192.168.1.157 -- renewal in 38792 seconds.