Cisco 3560实现DHCP中继代理

案例描述：

某公司的网络中有一个三层交换机SW1, 在公司的网络中每个部门一个VLAN、服务器一个独立的VLAN.在如图所示的环境中：
◆ Server处于VLAN10中，网段为192.168.1.0/24,其中DHCP服务的IP地址为192.168.1.2
◆ Sales部门处于VLAN20中，网段为192.168.2.0/24
◆ HR部门处于VLAN30中，网段为192.168.3.0/24

案例目的：
实现Sales和HR部门的所有的客户机能自动到DHCP服务上获得IP地址

案例注意点：
在部署环境的时候，所有的计算机使用微软的操作系统，其中 DHCP服务器使用微软的Windows  Server 2008 R2操作系统；交换机使用Cisco 3560三层交换机。

案例实现：
一.按照要求连接好网络设备。
二.网络配置

交换机的基本配置
Switch>enable
Switch#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
sw1(config)#hostname sw1
sw1(config)#no ip domain lookup
sw1(config)#line console 0
sw1(config-line)#exec-timeout 0 0
sw1(config-line)#logging synchronous

2.   创建VLAN
方法一：
SW1(config)#vlan 10
SW1(config-vlan)#name Server
SW1(config-vlan)#vlan 20
SW1(config-vlan)#name Sales
SW1(config-vlan)#vlan 30
SW1(config-vlan)#name HR

方法二：
SW1#vlan database
% Warning: It is recommended to configure VLAN from config mode,
  as VLAN database mode is being deprecated. Please consult user
  documentation for configuring VTP/VLAN in config mode.
SW1(vlan)#vlan 10 name Server
VLAN 10 modified:
    Name: Server
SW1(vlan)#vlan 20 name Sales
VLAN 20 modified:
    Name: Sales
SW1(vlan)#vlan 30 name HR
VLAN 30 modified:
    Name: HR
SW1(vlan)#exit
APPLY completed.
Exiting....

把相应的接口加入的相应VLAN中
SW1(config)#interface fastEthernet 0/4
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 10
SW1(config-if)#exit
SW1(config)#interface fastEthernet 0/5
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 20
SW1(config-if)#exit
SW1(config)#interface fastEthernet 0/6
SW1(config-if)#switchport mode access
SW1(config-if)#switchport access vlan 30

查看配置
SW1#sh vlan brief
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/1, Fa0/2, Fa0/3, Fa0/7
                                                Fa0/8, Fa0/9, Fa0/10, Fa0/11
                                                Fa0/12, Fa0/13, Fa0/14, Fa0/15
                                                Fa0/16, Fa0/17, Fa0/18, Fa0/19
                                                Fa0/20, Fa0/21, Fa0/22, Fa0/23
                                                Fa0/24
10   Server                           active    Fa0/4
20   Sales                             active    Fa0/5
30   HR                                active    Fa0/6
1002 fddi-default                  active   
1003 token-ring-default         active   
1004 fddinet-default              active   
1005 trnet-default                 active  

5.  配置SVI端口
SW1(config)#interface vlan 10
%LINK-5-CHANGED: Interface Vlan10, changed state to up
SW1(config-if)#ip address 192.168.1.1 255.255.255.0
SW1(config-if)#no shutdown
SW1(config-if)#int vlan 20
%LINK-5-CHANGED: Interface Vlan20, changed state to up
SW1(config-if)#ip address 192.168.2.1 255.255.255.0
SW1(config-if)#int vlan 30
%LINK-5-CHANGED: Interface Vlan30, changed state to up
SW1(config-if)#ip add 192.168.3.1 255.255.255.0
SW1(config-if)#no sh

验证
SW1#sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
      i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static route
       o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
C    192.168.1.0/24 is directly connected, Vlan10
C    192.168.2.0/24 is directly connected, Vlan20
C    192.168.3.0/24 is directly connected, Vlan30

为客户机所属VLAN配置中继代理
SW1(config)#int vlan 20
SW1(config-if)#ip helper-address 192.168.1.2
SW1(config-if)#int vlan 30
SW1(config-if)#ip helper-address 192.168.1.2