第3章OSPF-3.1 OSPF基础

3)非广播型多路访问网络类型NBMA

（1）R1、R2、R3 上做DLCI等配置

[R1]interface Serial 0/0/1
[R1-Serial0/0/1]link-protocol fr ietf //在接口封装帧中继
Warning: The encapsulation protocol of the link will be changed.
Continue? [Y/N]:y
[R1-Serial0/0/1]undo fr inarp //关闭反向的 ARP
[R1-Serial0/0/1]ip add 123.1.1.1 255.255.255.0
[R1-Serial0/0/1]fr map ip 123.1.1.2 102 broadcast //手动配置映射
[R1-Serial0/0/1]fr map ip 123.1.1.3 103 broadcast

[R2]interface Serial 0/0/2
[R2-Serial0/0/2]link-protocol fr ietf
[R2-Serial0/0/2]undo fr inarp
[R2-Serial0/0/2]ip add 123.1.1.2 255.255.255.0
[R2-Serial0/0/2]fr map ip 123.1.1.1 201 broadcast

[R3]interface Serial 0/0/3
[R3-Serial0/0/3]link-protocol fr ietf
[R3-Serial0/0/3]undo fr inarp
[R3-Serial0/0/3]ip add 123.1.1.3 255.255.255.0
[R3-Serial0/0/3]fr map ip 123.1.1.1 301 broadcast

（2）R1、R2、R3 上做OSPF配置

[R1]ospf 1 router-id 1.1.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]network 123.0.0.0 0.255.255.255

[R2]ospf 1 router-id 2.2.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 123.0.0.0 0.255.255.255

[R3]ospf 1 router-id 3.3.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]network 123.0.0.0 0.255.255.255

（3）由于默认的网络类型是 NBMA，手动指邻居，而且必两边都指定邻居

[R1]ospf 1 router-id 1.1.1.1
[R1-ospf-1]peer 123.1.1.2
[R1-ospf-1]peer 123.1.1.3

[R2]ospf 1 router-id 2.2.2.2
[R2-ospf-1]peer 123.1.1.1

[R3]ospf 1 router-id 3.3.3.3
[R3-ospf-1]peer 123.1.1.1

（4）在R2与R3上做二层的映射关系，使R2 与 R3 畅通

[R2-Serial0/0/2]fr map ip 123.1.1.3 201 broadcast
[R3-Serial0/0/3]fr map ip 123.1.1.2 301 broadcast

（5）测试

[R1]ping 3.3.3.3
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=255 time=40 ms
<R2>ping 1.1.1.1
Reply from 1.1.1.1: bytes=56 Sequence=1 ttl=255 time=30 ms
<R2>ping 3.3.3.3
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=254 time=60 ms
<R3>ping 2.2.2.2
Reply from 2.2.2.2: bytes=56 Sequence=1 ttl=254 time=30 ms

4）点对多点式网络类型P2MP

（1）在 R1、R2、R3 上修改接口的 OSPF 网络类型

[R1]interface  Serial 0/0/1
[R1-Serial0/0/1]ospf network-type p2mp

[R2]interface Serial0/0/2
[R2-Serial0/0/2]ospf network-type p2mp 

[R3]interface Serial 0/0/3
[R3-Serial0/0/3]ospf network-type p2mp 

（2）查看邻居表，没有了 DR/BDR 的选举

 OSPF Process 1 with Router ID 1.1.1.1
                 Neighbors 

 Area 0.0.0.0 interface 123.1.1.1(Serial0/0/1)'s neighbors
 Router ID: 2.2.2.2          Address: 123.1.1.2       
   State: Full  Mode:Nbr is  Master  Priority: 0
   DR: None   BDR: None   MTU: 0    
   Dead timer due in 96  sec 
   Retrans timer interval: 5 
   Neighbor is up for 00:00:53     
   Authentication Sequence: [ 0 ] 

 Router ID: 3.3.3.3          Address: 123.1.1.3       
   State: Full  Mode:Nbr is  Master  Priority: 0
   DR: None   BDR: None   MTU: 0    
   Dead timer due in 92  sec 
   Retrans timer interval: 5 
   Neighbor is up for 00:00:25     
   Authentication Sequence: [ 0 ] 

[R2-Serial0/0/2]display ospf interface Serial 0/0/2
         OSPF Process 1 with Router ID 2.2.2.2
                 Interfaces 
 Interface: 123.1.1.2 (Serial0/0/2)
 Cost: 1562    State: P-2-P     Type: P2MP      MTU: 1500  
 Timers: Hello 30 , Dead 120 , Poll  120 , Retransmit 5 , Transmit Delay 1 

（3）在修改为NMBA，进行查看

[R1-Serial0/0/2]ospf network-type nbma 
[R2-Serial0/0/2]display ospf interface Serial 0/0/2
         OSPF Process 1 with Router ID 2.2.2.2
                 Interfaces 
 Interface: 123.1.1.2 (Serial0/0/2)
 Cost: 1562    State: DROther    Type: NBMA      MTU: 1500  
 Priority: 0
 Designated Router: 123.1.1.1
 Backup Designated Router: 0.0.0.0
 Timers: Hello 30 , Dead 120 , Poll  120 , Retransmit 5 , Transmit Delay 1 

5）点到点的子接口网络类型

（1）R1、R2、R3子接口DLCI等配置

[R1]interface LoopBack 0
[R1-LoopBack0]ip address 1.1.1.1 32
[R1]interface Serial 0/0/1 
[R1-Serial0/0/1]link-protocol fr
Warning: The encapsulation protocol of the link will be changed. 
Continue? [Y/N]:y
[R1]interface Serial 0/0/1.12  
[R1-Serial0/0/1.12]ip address 12.1.1.1 8
[R1-Serial0/0/1.12]fr dlci 102
[R1]interface Serial 0/0/1.13
[R1-Serial0/0/1.13]ip address 13.1.1.1 8
[R1-Serial0/0/1.13]fr dlci 103

[R2]interface LoopBack 0
[R2-LoopBack0]ip address 2.2.2.2 32
[R2]interface Serial 0/0/2
[R2-Serial0/0/2]link-protocol fr
Warning: The encapsulation protocol of the link will be changed. 
Continue? [Y/N]:y
[R2]interface Serial 0/0/2.12
[R2-Serial0/0/2.12]ip address 12.1.1.2 8
[R2-Serial0/0/2.12]fr dlci 201

[R3]interface LoopBack 0
[R3-LoopBack0]ip address 3.3.3.3 32
[R3]interface Serial 0/0/3
[R3-Serial0/0/3]link-protocol fr
Warning: The encapsulation protocol of the link will be changed. 
Continue? [Y/N]:y
[R3]interface Serial 0/0/3.13 
[R3-Serial0/0/3.13]ip address 13.1.1.3 255.0.0.0
[R3-Serial0/0/3.13]fr dlci 301

（2）配置OSPF

[R1]ospf 1 router-id 1.1.1.1
[R1-ospf-1]area 0
[R1-ospf-1-area-0.0.0.0]network 1.1.1.1 0.0.0.0
[R1-ospf-1-area-0.0.0.0]network 12.0.0.0 0.255.255.255
[R1-ospf-1-area-0.0.0.0]network 13.0.0.0 0.255.255.255

[R2]ospf 1 router-id 2.2.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 12.0.0.0 0.255.255.255

[R3]ospf 1 router-id 3.3.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]network 13.0.0.0 0.255.255.255  

（3）查看接口的网络类型，将NBMA类型修改为所以需要点到点网络类型

Error: Wrong parameter found at '^' position.
[R1]display ospf interface Serial 0/0/1.12        
 Interface: 12.1.1.1 (Serial0/0/1.12)
 Cost: 1562    State: DR        Type: NBMA      MTU: 1500  
 Priority: 1
 Designated Router: 12.1.1.1
 Backup Designated Router: 0.0.0.0
 Timers: Hello 30 , Dead 120 , Poll  120 , Retransmit 5 , Transmit Delay 1 

[R1]interface Serial 0/0/1.12
[R1-Serial0/0/1.12]ospf network-type p2p 
[R1]interface Serial 0/0/1.13
[R1-Serial0/0/1.13]ospf network-type p2p 
[R2]interface Serial 0/0/2.12
[R2-Serial0/0/2.12]ospf network-type p2p 
[R3]interface Serial 0/0/3.13
[R3-Serial0/0/3.13]ospf network-type p2p

（4）查看OSPF 路由表

[R1]display ip routing-table protocol ospf
Destination/Mask    Proto   Pre  Cost      Flags NextHop         Interface
2.2.2.2/32  OSPF    10   1562        D   12.1.1.2        Serial0/0/1.12
3.3.3.3/32  OSPF    10   1562        D   13.1.1.3        Serial0/0/1.13

（5）测试

[R1]ping 2.2.2.2
Reply from 2.2.2.2: bytes=56 Sequence=1 ttl=255 time=50 ms
[R1]ping 3.3.3.3
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=255 time=60 ms
[R2]ping 3.3.3.3
Reply from 3.3.3.3: bytes=56 Sequence=1 ttl=254 time=80 ms
[R3]ping 2.2.2.2
Reply from 2.2.2.2: bytes=56 Sequence=1 ttl=254 time=60 ms

8.DR和BDR的概念

为减少网络中OSPF邻接关系数量，同时减少不必要的协议流量，OSPF会在MA网络（Multiple-Access多路访问）中选举DR（指定路由器）和BDR（备用指定路由器），不是DR和BDR的路由器为DRother，MA网络中DRother只和DR和BDR建立邻接关系，DR和BDR之间也建立邻接关系。DR负责侦听网络拓扑更新并及时通知其他路由器，BDR会监听DR状态，如有故障则接替DR工作。DR和BDR是通过Hello报文（DR优先级）实现的，优先级取值范围0-255，优先级为0的接口不具备DR和BDR选举资格，ospf dr-priority修改优先级，优先级高的成为DR，优先级相等时Router-ID大的成为DR，BDR选举类似。

使用Display ospf interface （GigabitEthernet 0/0/0）命令查看OSPF信息。

9.区域概念和多区域部署

1）一系列连续的OSPF路由器组成的网络称为OSPF域，域内路由器拥有相同的LSDB，确保网络信息一致。为减少网络规模太大，OSPF引入区域（Area）概念，域内划分不同区域，每个区域都有一个编号，采用点分十进制标识，骨干区域为Area0，只能有一个Area0，任何非骨干区域必须与Area0相连，介于骨干区域和非骨干区域之间的路由器称为ABR。

2）非骨干区域与骨干区域不相连，采用OSPF虚电路（Virtual Link）解决。R2与R3之间建立虚电路解决不相连问题。

10.OSPF路由器的角色

1）内部路由器IR

所有接口在同一个区域内,R1、R4、R5。

2）区域边界路由器ABR

接入多个区域的路由器，并且至少一个接口在Area0内，R2、R3。

3）骨干路由器BR

接入Area0的路由器，R1、R2、R3、R6。

4）AS边界路由器

在AS边界的路由器，R6。

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