OSPF協議的基礎配置及應用

首先進行IP地址劃分，如下圖

給每個路由器先配置環回地址

[r1]interface LoopBack 0
[r1-LoopBack0]ip add 192.168.1.1 27
[r1-LoopBack0]q
[r2]interface LoopBack 0
[r2-LoopBack0]ip add 192.168.1.65 27
[r2-LoopBack0]q
[r3]interface LoopBack 0
[r3-LoopBack0]ip add 192.168.1.97 27
[r3-LoopBack0]q
[r4]interface LoopBack 0
[r4-LoopBack0]ip add 4.4.4.4 24
[r4-LoopBack0]q

然后配置埠IP

[r1]interface GigabitEthernet 0/0/0
[r1-GigabitEthernet0/0/0]ip add 192.168.1.33 27
[r2]interface GigabitEthernet 0/0/0
[r2-GigabitEthernet0/0/0]ip add 192.168.1.34 27
[r3]interface GigabitEthernet 0/0/0
[r3-GigabitEthernet0/0/0]ip add 192.168.1.35 27
[r3-GigabitEthernet0/0/0]q
[r3]interface GigabitEthernet 0/0/1
[r3-GigabitEthernet0/0/1]ip add 192.168.1.129 27
[r4]interface GigabitEthernet 0/0/0
[r4-GigabitEthernet0/0/0]ip add 192.168.1.130 27

之后在每個路由器介面處進行ospf配置，并且在ABR上進行路由匯總，減少路由條目

[r1]ospf 1 router-id 1.1.1.1	
[r1-ospf-1]area 0
[r1-ospf-1-area-0.0.0.0]network 192.168.1.1 0.0.0.31
[r1-ospf-1-area-0.0.0.0]network 192.168.1.33 0.0.0.31
[r1-ospf-1-area-0.0.0.0]q
[r2]ospf 1 router-id 2.2.2.2
[r2-ospf-1]area 0
[r2-ospf-1-area-0.0.0.0]network 192.168.1.65 0.0.0.31
[r2-ospf-1-area-0.0.0.0]network 192.168.1.34 0.0.0.31
[r2-ospf-1-area-0.0.0.0]q
[r3]ospf 1 router-id 3.3.3.3
[r3]ospf 1
[r3-ospf-1]area 0
[r3-ospf-1-area-0.0.0.0]network 192.168.1.97 0.0.0.31
[r3-ospf-1-area-0.0.0.0]network 192.168.1.35 0.0.0.31
[r3-ospf-1-area-0.0.0.0]abr-summary 192.168.1.0 255.255.255.128
[r3-ospf-1-area-0.0.0.0]q
[r3-ospf-1]area 1
[r3-ospf-1-area-0.0.0.1]network 192.168.1.129 0.0.0.31
[r3-ospf-1-area-0.0.0.1]abr-summary 192.168.1.128 255.255.255.224
[r3-ospf-1-area-0.0.0.1]q
[r4]ospf 1 router-id 4.4.4.4
[r4-ospf-1]area 1
[r4-ospf-1-area-0.0.0.1]network 192.168.1.130 0.0.0.31
[r4-ospf-1-area-0.0.0.1]q

由于不能在R4上宣告環回，并且要求全網可達，所以在邊界路由器上ospf1中設定預設路由

[r4-ospf-1]default-route-advertise always 

R1-R3中要求R3是DR設備并且無BDR，只需要在R1,R2的介面上將優先級改為0即可

[r1]interface GigabitEthernet 0/0/0
[r1-GigabitEthernet0/0/0]ospf dr-priority 0
[r2]interface GigabitEthernet 0/0/0
[r2-GigabitEthernet0/0/0]ospf dr-priority 0

配置后如下所示R3為DR設備并且無BDR

[r3]display  ospf peer 

	 OSPF Process 1 with Router ID 3.3.3.3
		 Neighbors 

 Area 0.0.0.0 interface 192.168.1.35(GigabitEthernet0/0/0)'s neighbors
 Router ID: 1.1.1.1          Address: 192.168.1.33    
   State: Full  Mode:Nbr is  Slave  Priority: 0
   DR: 192.168.1.35  BDR: None   MTU: 0    
   Dead timer due in 33  sec 
   Retrans timer interval: 5 
   Neighbor is up for 00:00:57     
   Authentication Sequence: [ 0 ] 

 Router ID: 2.2.2.2          Address: 192.168.1.34    
   State: Full  Mode:Nbr is  Slave  Priority: 0
   DR: 192.168.1.35  BDR: None   MTU: 0    
   Dead timer due in 40  sec 
   Retrans timer interval: 6 
   Neighbor is up for 00:00:39     
   Authentication Sequence: [ 0 ] 

為了保障更新安全需要在每個介面處配置ospf認證，鄰居間的密碼，模式，編號必須都一樣，配置如下

[r1]interface GigabitEthernet 0/0/0
[r1-GigabitEthernet0/0/0]ospf authentication-mode  md5 1 cipher 123456
[r2]interface GigabitEthernet 0/0/0
[r2-GigabitEthernet0/0/0]ospf authentication-mode  md5 1 cipher 123456
[r3]interface GigabitEthernet 0/0/0
[r3-GigabitEthernet0/0/0]ospf authentication-mode  md5 1 cipher 123456
[r3-GigabitEthernet0/0/0]q
[r3]interface GigabitEthernet 0/0/1
[r3-GigabitEthernet0/0/1]ospf authentication-mode  md5 1 cipher 123456
[r4]interface GigabitEthernet 0/0/0
[r4-GigabitEthernet0/0/0]ospf authentication-mode  md5 1 cipher 123456

為了防止環路的出現，在每臺路由器上配置一個空介面路由

[r1]ip route-static 192.168.1.0 27 NULL 0
[r2]ip route-static 192.168.1.64 27 NULL 0
[r3]ip route-static 192.168.1.96 27 NULL 0
[r4]ip route-static 192.168.1.128 27 NULL 0

此時這個實驗完美結束