学习日记——（路由与交换技术）OSPF协议

一、相关知识

1、基本概念

1. OSPF是一个内部网关协议，用于单一自治系统内决策路由
2. OSPF是链路状态路由协议
3. OSPF通过路由器之间通告网络接口的状态来建立链路状态数据库，生成最短路径树，每个OSPF路由器使用这些最短路径构造路由表
4. OSPF路由器利用最短路径优先算法（SPF），独立地计算出到达任意目的地的路由
5. OSPF协议引入“分层路由”的概念，将网络分割成一个“主干”连接的一组相互独立的部分，这些相互独立的部分被称为“区域”，“主干”的部分称为“主干区域”。

2、协议操作

1. 建立路由器的邻接关系：OSPF路由器以交换路由器信息为目的，在所选择的相邻路由器之间建立的一种关系。
2. 发现路由器：路由器与路由器之间首先利用Hello报文的ID信息确认主从关系，然后主从路由器相互交换部分链路状态信息。
3. 选择适当的路由器：当一个路由器拥有完整独立的链路状态数据库，将采用SPF算法计算并创建路由表。OSPF利用量度计算目的路径，Cost最小者即为最短路径。如：链路带宽（主要）、时延或经济上的费用（可以忽略不计）。
4. 维护路由信息：当链路状态发生变化时，OSPF通过Flooding过程通告网络上其他路由器。当路由器接收到更新报文，就会更新自己的链路状态数据库。（注：当链路状态没有发生改变，OSPF路由信息也会自动更新，默认时间为30分钟）。

3、OSPF优缺点

1. OSPF是真正的LOOP-FREE（无路由自环）路由协议
2. OSPF收敛速度快，能够在最短的时间内将路由变化传递到整个自治系统
3. 区域划分的概念，可以更方便管提出理网络，网络信息也不会随规模扩大一下子就膨胀（注：区域划分时，分区须与骨干区相连）
4. 将协议自身的开销控制到最小
5. 通过严格划分路由的级别（共分4级），提供更可信的路由选择
6. OSPF支持基于接口的明文及MD5验证
7. OSPF适应各种规模的网络，最多可达数千台。
8. 缺点：配置相对复杂，路由负载均衡能力较弱。

二、例子

1、简单拓扑

注意：其他区域需要与骨干网有直接连接，如果有区域没跟骨干网“直接”相连是不行的

2、相关配置

R1：

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host R1

R1(config)#int g 0/0

R1(config-if)#ip add

R1(config-if)#ip address 192.168.1.254 255.255.255.0

R1(config-if)#no sh

R1(config-if)#no shutdown

R1(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up

R1(config-if)#e

R1(config-if)#exit

R1(config)#int g 0/1

R1(config-if)#ip address 192.168.12.1 255.255.255.0

R1(config-if)#no shutdown

R1(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/1, changed state to up

R1(config-if)#e

R1(config)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up

R1(config)#route os                  配置OSPF协议

R1(config)#route ospf 1

R1(config-router)#net

R1(config-router)#network 192.168.1.0 0.0.0.255 area 1

R1(config-router)#network 192.168.12.0 0.0.0.255 area 0

R1(config-router)#

00:13:15: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.23.1 on GigabitEthernet0/1 from LOADING to FULL, Loading Done

R1(config-router)#end

R1#

%SYS-5-CONFIG_I: Configured from console by console

R1#show ip route  启用OSPF后的路由表 O代表OSPF

Codes: L - local, 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, E - EGP

i - IS-IS, 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

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/24 is directly connected, GigabitEthernet0/0

L 192.168.1.254/32 is directly connected, GigabitEthernet0/0

O IA 192.168.2.0/24 [110/2] via 192.168.12.2, 00:05:54, GigabitEthernet0/1

O IA 192.168.3.0/24 [110/3] via 192.168.12.2, 00:02:52, GigabitEthernet0/1

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.12.0/24 is directly connected, GigabitEthernet0/1

L 192.168.12.1/32 is directly connected, GigabitEthernet0/1

O IA 192.168.23.0/24 [110/2] via 192.168.12.2, 00:05:27, GigabitEthernet0/1

R1#conf t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#int g 0/1     启用认证（也就是设密码）

R1(config-if)#ip ospf

R1(config-if)#ip ospf authentication m

R1(config-if)#ip ospf authentication message-digest ?

R1(config-if)#ip ospf authentication message-digest  （启用MD5认证)

R1(config-if)#ip ospf authenttication-key ?

% Unrecognized command

R1(config-if)#ip ospf authenttication-key

00:22:37: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.23.1 on GigabitEthernet0/1 from FULL to DOWN, Neighbor Down: Dead timer expired

00:22:37: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.23.1 on GigabitEthernet0/1 from FULL to DOWN, Neighbor Down: Interface down or detached （提示信息）

% Invalid input detected at '^' marker. 

R1(config-if)#ip ospf authentication-key 123456 

R1(config-if)#end

R1#

%SYS-5-CONFIG_I: Configured from console by console

R1#show ip route   启用认证后的路由表，因为R2的0/1接口没有配置相同的认证，所以数据到不了路由器2，注：两边的密码也需要相同

Codes: L - local, 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, E - EGP

i - IS-IS, 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

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/24 is directly connected, GigabitEthernet0/0

L 192.168.1.254/32 is directly connected, GigabitEthernet0/0

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.12.0/24 is directly connected, GigabitEthernet0/1

L 192.168.12.1/32 is directly connected, GigabitEthernet0/1

R1#

00:24:07: %OSPF-5-ADJCHG: Process 1, Nbr 192.168.23.1 on GigabitEthernet0/1 from LOADING to FULL, Loading Done

R1#show ip route     R2的0/1接口配置后MD5认证后的路由表

Codes: L - local, 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, E - EGP

i - IS-IS, 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

192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.1.0/24 is directly connected, GigabitEthernet0/0

L 192.168.1.254/32 is directly connected, GigabitEthernet0/0

O IA 192.168.2.0/24 [110/2] via 192.168.12.2, 00:01:13, GigabitEthernet0/1

O IA 192.168.3.0/24 [110/3] via 192.168.12.2, 00:01:13, GigabitEthernet0/1

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.12.0/24 is directly connected, GigabitEthernet0/1

L 192.168.12.1/32 is directly connected, GigabitEthernet0/1

O IA 192.168.23.0/24 [110/2] via 192.168.12.2, 00:01:13, GigabitEthernet0/1

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R2：

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host

Router(config)#host R2

R2(config)#int g 0/0

R2(config-if)#ip add

R2(config-if)#ip address 192.168.2.254 255.255.255.0

R2(config-if)#no sh

R2(config-if)#no shutdown

R2(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up

R2(config-if)#e

R2(config-if)#exit

R2(config)#int g 0/1

R2(config-if)#ip address 192.168.12.2 255.255.255.0

R2(config-if)#no shutdown

R2(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/1, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/1, changed state to up

R2(config-if)#e

R2(config)#int g 0/2

R2(config-if)#ip address 192.168.23.1 255.255.255.0

R2(config-if)#no shutdown

R2(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/2, changed state to up

R2(config-if)#e

R2(config)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up

R2(config)#route osp   配置OSPF

R2(config)#route ospf 2

R2(config-router)#net

R2(config-router)#network 192.168.2.0 0.0.0.255 area 2

R2(config-router)#network 192.168.12.0 0.0.0.255 area 0

R2(config-router)#network 192.168.23.0 0.0.0.255 area 3

00:13:13: %OSPF-5-ADJCHG: Process 2, Nbr 192.168.12.1 on GigabitEthernet0/1 from LOADING to FULL, Loading Done

R2(config-router)#do show ip route

Codes: L - local, 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, E - EGP

i - IS-IS, 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

O IA 192.168.1.0/24 [110/2] via 192.168.12.1, 00:00:31, GigabitEthernet0/1

192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.2.0/24 is directly connected, GigabitEthernet0/0

L 192.168.2.254/32 is directly connected, GigabitEthernet0/0

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.12.0/24 is directly connected, GigabitEthernet0/1

L 192.168.12.2/32 is directly connected, GigabitEthernet0/1

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.23.0/24 is directly connected, GigabitEthernet0/2

L 192.168.23.1/32 is directly connected, GigabitEthernet0/2

R2(config-router)#

00:16:11: %OSPF-5-ADJCHG: Process 2, Nbr 192.168.23.2 on GigabitEthernet0/2 from LOADING to FULL, Loading Done

00:22:28: %OSPF-5-ADJCHG: Process 2, Nbr 192.168.12.1 on GigabitEthernet0/1 from FULL to DOWN, Neighbor Down: Dead timer expired

00:22:28: %OSPF-5-ADJCHG: Process 2, Nbr 192.168.12.1 on GigabitEthernet0/1 from FULL to DOWN, Neighbor Down: Interface down or detached

R2(config-router)#e

R2(config)#int g 0/1    启用MD5认证

R2(config-if)#ip ospf authentication m

R2(config-if)#ip ospf authentication message-digest

R2(config-if)#ip ospf

00:24:05: %OSPF-5-ADJCHG: Process 2, Nbr 192.168.12.1 on GigabitEthernet0/1 from LOADING to FULL, Loading Done

% Incomplete command. (这是提示信息，再配置的过程中会出现)

R2(config-if)#ip ospf authentication-key 123456 （密码需跟前面的一样）

R2(config-if)#end

R2#

%SYS-5-CONFIG_I: Configured from console by console

R2#show ip route

Codes: L - local, 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, E - EGP

i - IS-IS, 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

O IA 192.168.1.0/24 [110/2] via 192.168.12.1, 00:00:48, GigabitEthernet0/1

192.168.2.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.2.0/24 is directly connected, GigabitEthernet0/0

L 192.168.2.254/32 is directly connected, GigabitEthernet0/0

O 192.168.3.0/24 [110/2] via 192.168.23.2, 00:08:42, GigabitEthernet0/2

192.168.12.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.12.0/24 is directly connected, GigabitEthernet0/1

L 192.168.12.2/32 is directly connected, GigabitEthernet0/1

192.168.23.0/24 is variably subnetted, 2 subnets, 2 masks

C 192.168.23.0/24 is directly connected, GigabitEthernet0/2

L 192.168.23.1/32 is directly connected, GigabitEthernet0/2

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R3：

Router>en

Router#conf t

Enter configuration commands, one per line. End with CNTL/Z.

Router(config)#host

Router(config)#host R3

R3(config)#int g 0/0

R3(config-if)#ip add

R3(config-if)#ip address 192.168.3.254 255.255.255.0

R3(config-if)#no sh

R3(config-if)#no shutdown

R3(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/0, changed state to up

R3(config-if)#e

R3(config-if)#exit

R3(config)#int g 0/2

R3(config-if)#ip address 192.168.23.2 255.255.255.0

R3(config-if)#no shutdown

R3(config-if)#

%LINK-5-CHANGED: Interface GigabitEthernet0/2, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet0/2, changed state to up

R3(config-if)#e

R3(config)#route os  配置OSPF

R3(config)#route ospf 3

R3(config-router)#net

R3(config-router)#network 192.168.23.0 0.0.0.255 area 3

R3(config-router)#network 192.168.3.0 0.0.0.255 area 3

R3(config-router)#

00:16:33: %OSPF-5-ADJCHG: Process 3, Nbr 192.168.23.1 on GigabitEthernet0/2 from LOADING to FULL, Loading Done

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注：OSPF 的认证给链路上的数据传输提供了安全保护，需要注意的是同一链路上的密码需要设置一样，例如上面 R1的0/1接口和R2的0/1接口相连，这时两者都需要配置MD5认证，否则链路时不通的，再来，两者的密码也需一致。

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这篇文章就到这里啦，上面就是有关OSPF协议的配置和认证。

如果有哪里写的不好，感谢指出来。

加油加油！