一、实验拓扑

二、实验需求

1、R1、R2、R3都是各自网络的网关设备
2、通过OSPF动态路由协议实现网络之间互联互通
3、R1-R3配置OSPF认证(R1的1口配置接口认证，R3的1口配置区域认证)，R1-R2配置接口认证，R2-R3配置OSPF认证（R2的2口配置接口认证，R3的3口配置区域认证）
4、假设R1为所有网络的出口，在R1上下发默认路由
5、通过修改cost值来改变R1-R2的路径为R1-R3-R2.

三、实验说明

这里的Loopback口用作OSPF的Router-id.

四、实验配置

1、设备命名
[Huawei]sysname R1
[Huawei]sysname R2
[Huawei]sysname R3
2、配置各自接口地址
[R1-GigabitEthernet0/0/1]ip address 10.0.13.1 24
[R1-GigabitEthernet0/0/3]ip address 10.0.12.1 24
[R1-LoopBack0]ip address 10.0.1.1 32
[R2-GigabitEthernet0/0/3]ip address 10.0.12.2 24
[R2-GigabitEthernet0/0/2]ip address 10.0.23.2 24
[R2-LoopBack0]ip address 10.0.1.2 32
[R3-GigabitEthernet0/0/1]ip address 10.0.13.3 24
[R3-GigabitEthernet0/0/3]ip address 10.0.23.3 24
[R3-LoopBack0]ip address 10.0.1.3 32
3、OSPF基本配置
R1配置
ospf 1
area 0.0.0.0
network 10.0.13.1 0.0.0.0
network 10.0.12.1 0.0.0.0
network 10.0.1.1 0.0.0.0
R2配置
ospf 1
area 0.0.0.0
network 10.0.1.2 0.0.0.0
network 10.0.12.2 0.0.0.0
network 10.0.23.2 0.0.0.0
R3配置
ospf 1
area 0.0.0.0
network 10.0.1.3 0.0.0.0
network 10.0.23.3 0.0.0.0
network 10.0.13.3 0.0.0.0
4、查看OSPF邻居状态
[R2]display ospf peer brief

          OSPF Process 1 with Router ID 10.0.1.2
          Peer Statistic Information
 -----------------------------------------------------------------------    
Area Id          Interface                        Neighbor id      State    
0.0.0.0          GigabitEthernet0/0/2             10.0.1.3         Full        
0.0.0.0          GigabitEthernet0/0/3             10.0.1.1         Full        
-----------------------------------------------------------------------

5、配置OSPF认证
[R1-GigabitEthernet0/0/1]ospf authentication-mode md5 1 cipher HCIA-Datacom
[R1-GigabitEthernet0/0/3]ospf authentication-mode md5 1 cipher HCIA-Datacom
[R2-GigabitEthernet0/0/2]ospf authentication-mode md5 1 cipher HCIA-Datacom
[R2-GigabitEthernet0/0/3]ospf authentication-mode md5 1 cipher HCIA-Datacom
[R3-ospf-1-area-0.0.0.0]authentication-mode md5 1 cipher HCIA-Datacom
6、验证认证结果
[R2]display ospf peer brief

          OSPF Process 1 with Router ID 10.0.1.2
          Peer Statistic Information
 -----------------------------------------------------------------------    
Area Id          Interface                        Neighbor id      State    
0.0.0.0          GigabitEthernet0/0/2             10.0.1.3         Full        
0.0.0.0          GigabitEthernet0/0/3             10.0.1.1         Full        
-----------------------------------------------------------------------

7、R1配置默认路由
[R1-ospf-1]default-route-advertise always
8、修改R1接口开销值来改变路径
[R1-GigabitEthernet0/0/3]ospf cost 5
配置前
[R1]tracert -a 10.0.1.1 10.0.1.2

traceroute to 10.0.1.2(10.0.1.2), max hops: 30 ,packet length: 40,press CTRL_C
to break

1 10.0.12.2 40 ms 50 ms 30 ms
配置后
[R1]tracert -a 10.0.1.1 10.0.1.2

traceroute to 10.0.1.2(10.0.1.2), max hops: 30 ,packet length: 40,press CTRL_C
to break

1 10.0.13.3 70 ms 30 ms 30 ms

2 10.0.23.2 60 ms 60 ms 70 ms