DHCP中继服务器

设备需求：
DHCP-server RHEL5.5  eth0: 192.168.10.66/24 (VMWARE19)
    gw: 192.168.10.1
-----------------------------------------------------------------
DHCP-Relay RHEL5.5  eth0: 192.168.10.1/24 (VMWARE19)
    eth1: 192.168.30.1/24 (VMWARE3)
    eth2: 192.168.50.1/24 (VMWARE5)
    eth3: 192.168.70.1/24 (VMWARE7)
-----------------------------------------------------------------
XP一台作为测试用机器：分别调为VMWARE3/5/7,可以分别获取192.168.30.0/24
192.168.50.0/24 192.168.70.0/24 网段中的IP地址
====================================================
步骤一:(在DHCP-Server上的配置)
[root@dhcp-server ~]# 
[root@dhcp-server ~]# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:0C:29:18:AA:A3  
          inet addr:192.168.10.66  Bcast:192.168.10.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe18:aaa3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:6390 errors:0 dropped:0 overruns:0 frame:0
          TX packets:130 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5659813 (5.3 MiB)  TX bytes:15820 (15.4 KiB)
          Interrupt:59 Base address:0x2024
[root@dhcp-server ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.10.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     0      0        0 eth0
0.0.0.0         192.168.10.1    0.0.0.0         UG    0      0        0 eth0
=========================================================
[root@dhcp-server ~]# rpm -q dhcp （如果未安装，请先安装DHCP服务器rpm包）
dhcp-3.0.5-23.el5
[root@dhcp-server ~]# cat /usr/share/doc/dhcp-3.0.5/dhcpd.conf.sample > /etc/dhcpd.conf
[root@dhcp-server ~]# vi /etc/dhcpd.conf （DHCP配置如下）
ddns-update-style interim;
ignore client-updates;
        option subnet-mask              255.255.255.0;
        option domain-name-servers      202.106.0.20,8.8.8.8;
        option time-offset              -18000; # Eastern Standard Time
        default-lease-time 21600;
        max-lease-time 43200;
subnet 192.168.10.0 netmask 255.255.255.0 {
}
subnet 192.168.30.0 netmask 255.255.255.0 {
        option routers                  192.168.30.1;
        range dynamic-bootp 192.168.30.128 192.168.30.254;
}
subnet 192.168.50.0 netmask 255.255.255.0 {
        option routers                  192.168.50.1;
        range dynamic-bootp 192.168.50.128 192.168.50.254;
}
subnet 192.168.70.0 netmask 255.255.255.0 {
        option routers                  192.168.70.1;
        range dynamic-bootp 192.168.70.128 192.168.70.254;
}
=============================================
[root@dhcp-server ~]# service dhcpd start
启动 dhcpd：                                               [确定]
[root@dhcp-server ~]# chkconfig dhcpd on
=============================================

步骤二：（在DHCP-Relay上的配置）
-------------------------------------------------------------------
[root@localhost ~]# ip addr show
2: eth0: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:cf:0c:9c brd ff:ff:ff:ff:ff:ff
    inet 192.168.10.1/24 brd 192.168.10.255 scope global eth0
    inet6 fe80::20c:29ff:fecf:c9c/64 scope link 
       valid_lft forever preferred_lft forever
3: eth1: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:cf:0c:a6 brd ff:ff:ff:ff:ff:ff
    inet 192.168.30.1/24 brd 192.168.30.255 scope global eth1
    inet6 fe80::20c:29ff:fecf:ca6/64 scope link 
       valid_lft forever preferred_lft forever
4: eth2: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:cf:0c:b0 brd ff:ff:ff:ff:ff:ff
    inet 192.168.50.1/24 brd 192.168.50.255 scope global eth2
    inet6 fe80::20c:29ff:fecf:cb0/64 scope link 
       valid_lft forever preferred_lft forever
5: eth3: mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:0c:29:cf:0c:ba brd ff:ff:ff:ff:ff:ff
    inet 192.168.70.1/24 brd 192.168.70.255 scope global eth3
    inet6 fe80::20c:29ff:fecf:cba/64 scope link 
       valid_lft forever preferred_lft forever
----------------------------------------------------------------------
[root@dhcp-realy ~]# rpm -q dhcp （如果未安装，请先安装DHCP服务器rpm包）
dhcp-3.0.5-23.el5
[root@dhcp-realy ~]# vi /etc/sysctl.conf 
7 net.ipv4.ip_forward = 1  //此处将0改为1，开启路由转发功能
[root@dhcp-realy ~]# sysctl -p //使上面修改的内核参数生效
[root@dhcp-realy ~]# vi /etc/sysconfig/dhcrelay 
# Command line options here
INTERFACES="eth0 eth1 eth2 eth3" //此处指定DHCP-RELAY要侦听的网卡名称
DHCPSERVERS="192.168.10.66" //此处指定DHCP服务器的IP地址
=======================================================
[root@dhcp-realy ~]# service dhcrelay start
启动 dhcrelay：                                            [确定]
[root@dhcp-realy ~]# chkconfig dhcrelay on
[root@dhcp-realy ~]# dhcrelay 192.168.10.66    //如在虚拟机中演示本实验，本条命令必须要执行，
//表示立即在本机开启中继对DHCP服务的转发功能
Internet Systems Consortium DHCP Relay Agent V3.0.5-RedHat
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/
Listening on LPF/eth3/00:0c:29:cf:0c:ba
Sending on   LPF/eth3/00:0c:29:cf:0c:ba
Listening on LPF/eth2/00:0c:29:cf:0c:b0
Sending on   LPF/eth2/00:0c:29:cf:0c:b0
Listening on LPF/eth1/00:0c:29:cf:0c:a6
Sending on   LPF/eth1/00:0c:29:cf:0c:a6
Listening on LPF/eth0/00:0c:29:cf:0c:9c
Sending on   LPF/eth0/00:0c:29:cf:0c:9c
Sending on   Socket/fallback
=================================================
步骤三：
用XP来进行测试

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