DHCP概述
1)了解DHCP服务
DHCP(Dynimic Host Configuration Protocol,动态主机配置协议)是由IEIF(Internet工作任务小组)设计开发的,专门用于为TCP/IP网络的计算机自动分配TCP/IP参数的协议,DHCP服务避免了因手工设置IP地址所产生的错误,同时也避免了把一个IP地址分配给多台工作站所造成的地址冲突;DHCP提供了安全,可靠且简单的TCP/IP网络设置,降低了配置IP地址的负担
2)使用DHCP的好处
减少管理员的工作量
避免输入错误的可能
避免IP冲突
当网更改IP地址段时,不需要在重新配置每个用户的IP地址
提高了IP地址的利用率
方便客户端的配置
DHCP的工作原理
1)DHCP的分配方式
DHCP服务器提供了三种IP分配方式:自动分配、手动分配和动态分配
自动分配是当DHCP客户机第一次成功的从DHCP服务器获取到一个IP地址后,就永久地使用这个IP地址
手动分配是由DHCP服务器管理员专门指定IP地址
动态分配时当DHCP客户机第一次从DHCP服务器获取到IP地址后,并非永久地使用该地址,每次使用完后,DHCP客户机就需要释放这个IP地址,供其他客户机使用
2)DHCP的租约过程
客户机从DHCP服务器获得IP地址的过程称为DHCP的租约过程;租约过程分为四个步骤:
客户机请求IP地址(客户机发DHCP Discover广播包)
服务器响应(服务器发DHCP Offer广播包)
客户机选择IP地址(客户机发DHCP Request广播包)
服务器确定租约(服务器发DHCP ACK广播包)
1、客户端请求IP
DHCP Discover
2、服务器响应
DHCP Offer
3、客户机选择IP
DHCP Request
4、服务器确定租约
DHCP ACK
5、重新接入网络
dhcp软件安装
dhcp软件在系统镜像光盘里就已经提供了,只需要使用rpm或者yum软件安装即可
如果使用yum安装需要提前配置好yum
[root@localhost ~]# mkdir /mnt/cdrom [root@localhost ~]# mount /dev/cdrom /mnt/cdr [root@localhost ~]# cat /etc/yum.repos.d/base.repo [base] name=centos baseurl=file:///mnt/cdrom enabled=1 gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-$releasever [root@localhost ~]# rpm -ivh /mnt/cdrom/Packages/dhcp-4.2.5-42.el7.centos.x86_64.rpm 或者 [root@localhost ~]# yum install -y dhcp 使用下面的命令可以查看dhcp软件的介绍和安装生成文件及目录 [root@localhost ~]# yum info dhcp Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile Installed Packages Name : dhcp Arch : x86_64 Epoch : 12 Version : 4.2.5 Release : 42.el7.centos Size : 1.4 M Repo : installed Summary : Dynamic host configuration protocol software URL : http://isc.org/products/DHCP/ License : ISC Description : 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. : : 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. [root@localhost ~]# rpm -ql dhcp /etc/NetworkManager /etc/NetworkManager/dispatcher.d /etc/NetworkManager/dispatcher.d/12-dhcpd /etc/dhcp /etc/dhcp/dhcpd.conf /etc/dhcp/dhcpd6.conf /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
dhcp基本配置
前提条件:
DHCP服务器与客户端主机已正常连通,并在同一网络中
如果客户端主机使用了DHCP方式动态获取IP地址,而网络中没有DHCP服务器,或者服务器出现问题,则客户端就不能正常取得地址了;如果是Windows,它将从B类网段192.254.0.0中挑选一个IP地址作为自己的IP地址,并继续每隔5分钟尝试与DHCP服务器进行通信,一旦与DHCP取得通信,客户机将放弃自己配置的IP地址,使用DHCP服务器分配的IP地址;
1、DHCP服务器配置
DHCP服务器需要向客户端分配IP地址,服务器自身需要使用一个静态的IP地址
[root@localhost ~]# ifconfig eno16777736
eno16777736: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.16.1.10 netmask 255.255.0.0 broadcast 172.16.255.255
inet6 fe80::20c:29ff:fe65:8475 prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:65:84:75 txqueuelen 1000 (Ethernet)
RX packets 7051 bytes 6763047 (6.4 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1808 bytes 225665 (220.3 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@localhost ~]# vi /etc/dhcp/dhcpd.conf
...
option domain-name "bsg.com";
option domain-name-servers 202.106.0.20, 8.8.8.8,172.16.1.254;
default-lease-time 3600;
max-lease-time 7200;
...
subnet 172.16.1.0 netmask 255.255.0.0 {
range 172.16.1.100 172.16.1.200
}
...
[root@localhost ~]# systemctl start dhcpd.service
[root@localhost ~]# ss -tunl
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port
udp UNCONN 0 0 *:40620 *:*
udp UNCONN 0 0 *:67 *:*
udp UNCONN 0 0 :::18696 :::*
tcp LISTEN 0 128 *:22 *:*
tcp LISTEN 0 100 127.0.0.1:25 *:*
tcp LISTEN 0 128 :::22 :::*
tcp LISTEN 0 100 ::1:25 :::*
2、客户端主机配置
如果客户端之前使用静态的IP地址,需要将获取方式改为dhcp自动获取并删除IP地址,修改完配置文件后重新启动网卡
Linux客户端
Windows客户端
在DHCP服务器上查看IP地址分配及租约情况
[root@localhost ~]# 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 172.16.1.102 { starts 2 2016/11/01 13:55:33; ends 2 2016/11/01 13:57:51; tstp 2 2016/11/01 13:57:51; cltt 2 2016/11/01 13:55:33; binding state free; hardware ethernet 00:0c:29:96:ea:a9; uid "\001\000\014)\226\352\251"; } lease 172.16.1.100 { starts 2 2016/11/01 13:56:35; ends 2 2016/11/01 14:06:35; tstp 2 2016/11/01 14:06:35; cltt 2 2016/11/01 13:56:35; binding state active; next binding state free; rewind binding state free; hardware ethernet 00:0c:29:9d:3a:2a; } server-duid "\000\001\000\001\037\253K\017\000\014)e\204u";
为客户机保留IP地址
1、获取客户机的mac地址
2、修改DHCP的配置文件
mac地址不区分大小写,windows客户端的mac地址中的"-"需要换成":"
[root@master ~]# vi /etc/dhcp/dhcpd.conf ... host ftpsrv { hardware ethernet 00:0c:29:9d:3a:2a; fixed-address 172.16.1.253; } host winc1 { hardware ethernet 00:0c:29:96:ea:a9; fixed-address 172.16.1.50; } ... [root@localhost ~]# systemctl restart dhcpd.service [root@localhost ~]# ss -tnul Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port udp UNCONN 0 0 *:67 *:* udp UNCONN 0 0 *:31306 *:* udp UNCONN 0 0 :::45651 :::* tcp LISTEN 0 128 *:22 *:* tcp LISTEN 0 100 127.0.0.1:25 *:* tcp LISTEN 0 128 :::22 :::* tcp LISTEN 0 100 ::1:25 :::*
3、客户端重新获取IP地址
本文出自 “Linux路上” 博客,请务必保留此出处http://dreamlinuxc.blog.51cto.com/5733156/1868125
原文地址:http://dreamlinuxc.blog.51cto.com/5733156/1868125