为什么80%的码农都做不了架构师？>>> 
安装DHCP软件
[root@hding ~]# yum install dhcpDHCP配置文件有一定的格式
[root@hding ~]# cp /usr/share/doc/dhcp-3.0.5/dhcpd.conf.sample /etc/dhcpd.conf编辑dhcpd.conf主配置文件
[root@hding ~]# vi /etc/dhcpd.conf
1 ddns-update-style interim; 必需有
2 ignore client-updates;
3
4 subnet 192.168.0.0 netmask 255.255.255.0 { 192.168.0局部网段
5
6 # --- default gateway
7 option routers 192.168.0.111; 本机作为网关
8 option subnet-mask 255.255.255.0; 分配掩码
9
10 option nis-domain "hding.net"; NIS域
11 option domain-name "hding.net"; 域名
12 option domain-name-servers 192.168.0.111; 域名服务器IP
13
14 option time-offset -18000; # Eastern Standard Time
15 # option ntp-servers 192.168.0.1;
16 # option netbios-name-servers 192.168.1.1;
17 # --- Selects point-to-point node (default is hybrid). Don't change this unl
ess
18 # -- you understand Netbios very well
19 # option netbios-node-type 2;
20
21 range dynamic-bootp 192.168.0.128 192.168.0.253; 分配地址池
22 default-lease-time 21600; 租约时间6小时
23 max-lease-time 43200; 最大租约时间12小时
24
25 # we want the nameserver to appear at a fixed address
26 host ns { 给固定MAC固定IP，通常是服务器之类固定IP
27 next-server hding.net;
28 hardware ethernet 12:34:56:78:AB:CD;
29 fixed-address 192.168.0.254;
30 }
31 }
[root@hding ~]# service dhcpd restart
Starting dhcpd: [ OK ]client端测试: dhclient
server:
[root@hding ~]# tail -F /var/log/messages
Jan 14 08:05:58 hding dhcpd: DHCPDISCOVER from 00:50:56:25:94:05 via eth0
Jan 14 08:05:59 hding dhcpd: DHCPOFFER on 192.168.0.253 to 00:50:56:25:94:05 via eth0
Jan 14 08:05:59 hding dhcpd: DHCPREQUEST for 192.168.0.253 (192.168.0.111) from 00:50:56:25:94:05 via eth0
Jan 14 08:05:59 hding dhcpd: DHCPACK on 192.168.0.253 to 00:50:56:25:94:05 via eth0
[root@hding ~]# cat /var/lib/dhcpd/dhcpd.leases
lease 192.168.0.253 {
starts 3 2015/01/14 16:05:59;
ends 3 2015/01/14 22:05:59;
binding state active;
next binding state free;
hardware ethernet 00:50:56:25:94:05;
}server:
[root@hding ~]# tail -F /var/log/messages
Jan 14 08:36:58 hding dhcpd: DHCPDISCOVER from 12:34:56:78:ab:cd via eth0
Jan 14 08:36:58 hding dhcpd: DHCPOFFER on 192.168.0.254 to 12:34:56:78:ab:cd via eth0
Jan 14 08:36:58 hding dhcpd: DHCPREQUEST for 192.168.0.254 (192.168.0.111) from 12:34:56:78:ab:cd via eth0
Jan 14 08:36:58 hding dhcpd: DHCPACK on 192.168.0.254 to 12:34:56:78:ab:cd via eth0前面介绍的是给同一网段内的PC分配IP地址，由于广播包是允许跨网段的，而dhcp的第一个discovery包是广播包就过不了，那么每个网段 都要有一台DHCP服务器？dhcprelay就是为了解决跨网段问题而存在的，它接收到本网段client的discovery包，然后由它单播转给另 一个网段的DHCP server，而DHCP server回的包也通过dhcp relay再回给client，这样client虽然发了广播的discovery，但经过dhcp relay转一下变成了单播，跨网段成功
A作为server，分配 192.168.0.0 255.255.255.0
192.168.4.0 255.255.255.0
C作为router，转发路由器
D作为与B同网段的dhcp relay，B发的广播包由D接收转发给A，A回的包由D再转给B
A：
[root@hding ~]# vi /etc/dhcpd.conf
1 ddns-update-style interim;
2 ignore client-updates;
3
4 subnet 192.168.0.0 netmask 255.255.255.0 {
5
6 # --- default gateway
7 option routers 192.168.0.111;
8 option subnet-mask 255.255.255.0;
9
10 option nis-domain "hding.net";
11 option domain-name "hding.net";
12 option domain-name-servers 192.168.0.111;
13
14 option time-offset -18000; # Eastern Standard Time
15 # option ntp-servers 192.168.0.1;
16 # option netbios-name-servers 192.168.1.1;
18 # -- you understand Netbios very well
19 # option netbios-node-type 2;
20
21 range dynamic-bootp 192.168.0.128 192.168.0.253;
22 default-lease-time 21600;
23 max-lease-time 43200;
24
25 # we want the nameserver to appear at a fixed address
26 host ns {
27 next-server hding.net;
28 hardware ethernet 12:34:56:78:AB:CD;
29 fixed-address 192.168.0.254;
30 }
31 }
32
33 subnet 192.168.4.0 netmask 255.255.255.0 {
34 option routers 192.168.4.112;
35 option subnet-mask 255.255.255.0;
36 range dynamic-bootp 192.168.4.12 192.168.4.25;
37 default-lease-time 21600;
38 max-lease-time 43200;
39 }
route add -net 192.168.4.0 netmask 255.255.255.0 gw 192.168.0.112D:
[root@ding ~]# vi /etc/sysconfig/network-scripts/ifcfg-eth1
1 # Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE]
2 DEVICE=eth1
3 BOOTPROTO=none
4 ONBOOT=yes
5 IPADDR=192.168.4.1
6 NETMASK=255.255.255.0
7 GATEWAY=192.168.4.112
8 HWADDR=00:0c:29:52:73:72
[root@ding ~]# vi /etc/sysconfig/dhcrelay
1 # Command line options here
2 DHCRELAYARGS=""
3 INTERFACES="eth1"
4 DHCPSERVERS="192.168.0.111"C:
[root@dh network-scripts]# ifconfig
eth0 Link encap:Ethernet HWaddr 12:34:56:78:AB:CD
inet addr:192.168.0.112 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:591 errors:0 dropped:0 overruns:0 frame:0
TX packets:478 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:53371 (52.1 Kb) TX bytes:63627 (62.1 Kb)
Interrupt:5 Base address:0x2000
eth1 Link encap:Ethernet HWaddr 00:0C:29:1D:C2:01
inet addr:192.168.4.112 Bcast:192.168.4.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:168 (168.0 b)
Interrupt:5 Base address:0x2080
[root@dh network-scripts]# echo "1" > /proc/sys/net/ipv4/ip_forwardA log:
Jan 14 09:24:50 hding dhcpd: DHCPREQUEST for 192.168.0.252 from 00:0c:29:d0:f2:d2 (Julia) via 192.168.4.1: ignored (not authoritative).
Jan 14 09:24:58 hding last message repeated 2 times
Jan 14 09:25:06 hding dhcpd: DHCPDISCOVER from 00:0c:29:d0:f2:d2 via 192.168.4.1
Jan 14 09:25:07 hding dhcpd: DHCPOFFER on 192.168.4.25 to 00:0c:29:d0:f2:d2 (Julia) via 192.168.4.1
Jan 14 09:25:07 hding dhcpd: DHCPREQUEST for 192.168.4.25 (192.168.0.111) from 00:0c:29:d0:f2:d2 (Julia) via 192.168.4.1
Jan 14 09:25:07 hding dhcpd: DHCPACK on 192.168.4.25 to 00:0c:29:d0:f2:d2 (Julia) via 192.168.4.1