实验12: OSPF
实验9-1:单区域点到点链路的OSPF
实验目的
通过本实验可以掌握：
（1）在路由器上启动OSPF 路由进程
（2）启用参与路由协议的接口，并且通告网络及所在的区域
（3）度量值cost 的计算
（4）点到点链路上的OSPF 的特征
（5）查看和调试OSPF 路由协议相关信息
实验拓扑
实验步骤
n 步骤1：配置路由器R1
R1(config)#router ospf 110
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 1.1.1.0 0.0.0.255 area 0
R1(config-router)#network 192.168.12.0 0.0.0.255 area 0
R1(config-router)#network 192.168.13.0 0.0.0.255 area 0
n 步骤2：配置路由器R2
R2(config)#router ospf 110
R2(config-router)#router-id 2.2.2.2
R2(config-router)#network 192.168.12.0 0.0.0.255 area 0
R2(config-router)#network 2.2.2.0 0.0.0.255 area 0
n 步骤3：配置路由器R3
R3(config)#router ospf 110
R3(config-router)#router-id 3.3.3.3
R3(config-router)#network 192.168.13.0 0.0.0.255 area 0
R3(config-router)#network 3.3.3.0 0.0.0.255 area 0
实验调试
n show ip route
R1#show 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 192.168.12.0/24 is directly connected, Serial1/0
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
C 192.168.13.0/24 is directly connected, Serial1/1
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/65] via 192.168.12.2, 00:01:03, Serial1/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/65] via 192.168.13.3, 00:01:03, Serial1/1
输出结果表明同一个区域内通过OSPF 路由协议学习的路由条目用代码“O”表示
【说明】
① 环回接口OSPF 路由条目的掩码长度都是32 位，这是环回接口的特性，尽管通告了24 位，解决的办法是在环回接口下修改网络类型为“Point-to-Point”，操作如下：
R1(config)#interface loopback 0
R1(config-if)#ip ospf network point-to-point
R2(config)#interface loopback 0
R2(config-if)#ip ospf network point-to-point
R3(config)#interface loopback 0
R3(config-if)#ip ospf network point-to-point
这样收到的路由条目的掩码长度和通告的一致。
② 路由条目“3.3.3.3”的度量值为65，计算过程如下：
cost 的计算公式为10*8/带宽（bps），然后取整，而且是所有链路入口的cost 之和，环回接口的cost 为1，路由条目“3.3.3.3”到路由器R1经过的入接口包括路由器R3 的
loopback0 ， 路由器R1 的s1/1 ， 所以计算如下：
1+[10*8/1544000]=65。也可以直接通过命令“ip ospf cost”设置接口的cost
值，并且它是优先计算的cost 值的
n show ip protocols
R1#show ip pro
Routing Protocol is "ospf 110"
//当前路由器运行的OSPF 进程ID
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Router ID 1.1.1.1
//本路由器ID
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
//本路由器参与的区域数量和类型
Maximum path: 4
Routing for Networks:
1.1.1.0 0.0.0.255 area 0
192.168.12.0 0.0.0.255 area 0
192.168.13.0 0.0.0.255 area 0
//以上5 行表明路由信息源
Reference bandwidth unit is 100 mbps
//参考带宽为10*8
Routing Information Sources:
Gateway Distance Last Update
3.3.3.3 110 00:14:12
2.2.2.2 110 00:14:12
Distance: (default is 110)
//OSPF 路由协议默认的管理距离
n show ip ospf
该命令显示OSPF 进程及区域的细节，如路由器运行SPF 算法的次数等。
R1#sho ip ospf 110
Routing Process "ospf 110" with ID 1.1.1.1
Start time: 00:10:06.832, Time elapsed: 00:28:31.344
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
Router is not originating router-LSAs with maximum metric
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 0. Checksum Sum 0x000000
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Number of areas transit capable is 0
External flood list length 0
Area BACKBONE(0)
Number of interfaces in this area is 3
Area has no authentication
SPF algorithm last executed 00:17:36.024 ago
SPF algorithm executed 7 times
Area ranges are
Number of LSA 3. Checksum Sum 0x01A850
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
n show ip ospf interface
R1#show ip ospf interface
Loopback0 is up, line protocol is up
Internet Address 1.1.1.1/24, Area 0
Process ID 110, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT,
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Supports Link-local Signaling (LLS)
Index 3/3, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 0, maximum is 0
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Serial1/1 is up, line protocol is up
Internet Address 192.168.13.1/24, Area 0
//该接口的地址和运行的OSPF 区域
Process ID 110, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 64
//进程ID，路由器ID，网络类型，接口Cost 值
Transmit Delay is 1 sec, State POINT_TO_POINT,
//接口的延迟和状态
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
//显示几个计时器的
Hello due in 00:00:02
//距离下次发送Hello包的时间
Supports Link-local Signaling (LLS)
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 1, Adjacent neighbor count is 1
//邻居的个数以及已建立邻接关系的邻居的个数
Adjacent with neighbor 3.3.3.3
//已经建立邻接关系的邻居路由器ID
Suppress hello for 0 neighbor(s)
//没有进行Hello 抑制
n show ip ospf neighbor
R1#show ip ospf nei
Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/ - 00:00:34 192.168.13.3 Serial1/1
2.2.2.2 0 FULL/ - 00:00:34 192.168.12.2 Serial1/0
以上输出表明路由器R2 有两个邻居，它们的路由器ID 分别为1.1.1.1 和3.3.3.3,其
它参数解释如下：
① Pri：邻居路由器接口的优先级；
② State：当前邻居路由器接口的状态；
③ Dead Time：清除邻居关系前等待的最长时间；
④ Address：邻居接口的地址；
⑤ Interface：自己和邻居路由器相连接口；
⑥ “-”： 表示点到点的链路上OSPF 不进行DR 选举。
n show ip ospf database
R1#show ip ospf database
OSPF Router with ID (1.1.1.1) (Process ID 110)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 1891 0x80000007 0x005E97 5
2.2.2.2 2.2.2.2 396 0x80000003 0x00EF98 3
3.3.3.3 3.3.3.3 184 0x80000003 0x005623 3
以上输出是R1 的区域0 的拓扑结构数据库的信息，标题行的解释如下：
① Link ID：是指Link State ID,代表整个路由器，而不是某个链路；
② ADV Router：是指通告链路状态信息的路由器ID；
③ Age：老化时间；
④ Seq#：序列号；
⑤ Checksum：校验和；
⑥ Link count：通告路由器在本区域内的链路数目。
实验9-2:广播多路访问链路上的OSPF
实验目的
通过本实验可以掌握：
（1）在路由器上启动OSPF 路由进程
（2）启用参与路由协议的接口，并且通告网络及所在的区域
（3）修改参考带宽
（4）DR 选举的控制
（5）广播多路访问链路上的OSPF 的特征
实验拓扑
实验步骤
n 步骤1：配置路由器R1
R1(config)#int f0/0
R1(config-if)#ip add 192.168.1.1 255.255.255.0
R1(config-if)#no sh
R1(config-if)#int lo0
R1(config-if)#ip add 1.1.1.1 255.255.255.0
R1(config)#router ospf 110
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 1.1.1.0 0.0.0.255 area 0
R1(config-router)#network 192.168.1.0 0.0.0.255 area 0
n 步骤2：配置路由器R2
R2(config)#int f0/0
R2(config-if)#ip add 192.168.1.2 255.255.255.0
R2(config-if)#no sh
R2(config-if)#int lo0
R2(config-if)#ip add 2.2.2.2 255.255.255.0
R2(config)#router ospf 110
R2(config-router)#router-id 2.2.2.2
R2(config-router)#network 2.2.2.0 0.0.0.255 area 0
R2(config-router)#network 192.168.1.0 0.0.0.255 area 0
n 步骤3：配置路由器R3
R3(config)#int f0/0
R3(config-if)#ip add 192.168.1.3 255.255.255.0
R3(config-if)#no sh
R3(config-if)#int lo0
R3(config-if)#ip add 3.3.3.3 255.255.255.0
R3(config)#router ospf 110
R3(config-router)#router-id 3.3.3.3
R3(config-router)#network 3.3.3.0 0.0.0.255 area 0
R3(config-router)#network 192.168.1.0 0.0.0.255 area 0
n 步骤4：配置路由器R4
R4(config)#int f0/0
R4(config-if)#ip add 192.168.1.4 255.255.255.0
R4(config-if)#no sh
R4(config-if)#int lo0
R4(config-if)#ip add 4.4.4.4 255.255.255.0
R4(config)#router ospf 110
R4(config-router)#router-id 4.4.4.4
R4(config-router)#network 4.4.4.0 255.255.255.0 area 0
R4(config-router)#network 192.168.1.0 255.255.255.0 area 0
实验调试
n show ip ospf neighbor
R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
2.2.2.2 1 FULL/BDR 00:00:35 192.168.1.2 FastEthernet0/0
3.3.3.3 1 FULL/DROTHER 00:00:38 192.168.1.3 FastEthernet0/0
4.4.4.4 1 FULL/DROTHER 00:00:38 192.168.1.4 FastEthernet0/0
以上输出表明在广播多路访问网络中，R1是DR, R2是BDR, R3和R4 是DROTHER。
【技术要点】
1）为了避免路由器之间建立完全邻接关系而引起的大量开销，OSPF 要求在多路访问的网络中选举一个DR，每个路由器都与之建立邻接关系。选举DR 的同时也选举出一个BDR，在DR 失效的时候，BDR 担负起DR 的职责，而且所有其它路由器只与DR 和BDR 建立邻接关系；
2）DR 和BDR 有它们自己的组播地址224.0.0.6；
3）DR 和BDR 的选举是以各个网络为基础的，也就是说DR 和BDR 选举是一个路由器的接口特性，而不是整个路由器的特性；
4）DR 选举的原则：
① 首要因素是时间，最先启动的路由器被选举成DR；
② 如果同时启动，或者重新选举，则看接口优先级（范围为0-255），优先级最高的被选举成DR，默认情况下，多路访问网络的接口优先级为1，点到点网络接口优先级为0，修改接口优先级的命令是“ ip ospf priority”，如果接口的优先级被设置为0，那么该接口将不参与DR 选举；
③ 如果前两者相同，最后看路由器ID，路由器ID 最高的被选举成DR；
5）DR 选举是非抢占的，除非人为地重新选举。重新选举DR 的方法有两种，一是路由器重新启动，二是执行“clear ip ospf process”命令。
n show ip ospf interface
分别在路由器R1 和R4 上执行该命令：
R1#show ip ospf int f0/0
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.1.1/24, Area 0
Process ID 110, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
//自己state 是DR
Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
//DR 的路由器ID 以及接口地址
Backup Designated router (ID) 2.2.2.2, Interface address 192.168.1.2
//BDR 的路由器ID 以及接口地址
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:02
Supports Link-local Signaling (LLS)
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 3, Adjacent neighbor count is 3
//R1 是DR,有3 个邻居，并且全部形成邻接关系
Adjacent with neighbor 2.2.2.2 (Backup Designated Router) //R2 是BDR
Adjacent with neighbor 3.3.3.3
Adjacent with neighbor 4.4.4.4
Suppress hello for 0 neighbor(s)
R4#sh ip ospf int f0/0
FastEthernet0/0 is up, line protocol is up
Internet Address 192.168.1.4/24, Area 0
Process ID 110, Router ID 4.4.4.4, Network Type BROADCAST, Cost: 1
//网络类型为BROADCAST
Transmit Delay is 1 sec, State DROTHER, Priority 1
//自己的state 是DROTHER
Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
//DR 的路由器ID 和接口地址
Backup Designated router (ID) 2.2.2.2, Interface address 192.168.1.2
//BDR 的路由器ID 和接口地址
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:04
Supports Link-local Signaling (LLS)
Index 2/2, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 1
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 3, Adjacent neighbor count is 2
//有3 个邻居，只与R1 和R2 形成邻接关系，与R3 只是邻居关系
Adjacent with neighbor 1.1.1.1 (Designated Router)
Adjacent with neighbor 2.2.2.2 (Backup Designated Router)
//上面两行表示与DR 和BDR 形成邻接关系
Suppress hello for 0 neighbor(s)
从上面的路由器R1 和R4 的输出得知，邻居关系和邻接关系是不能混为一谈的，邻居关系是指达到2WAY 状态的两台路由器，而邻接关系是指达到FULL 状态的两台路由器。
（3）debug ip ospf adj
该命令显示OSPF 邻接关系创建或中断的过程。
R2#debug ip ospf adj
OSPF adjacency events debugging is on
R2#clear ip ospf process
Reset ALL OSPF processes? [no]: y
R2#
*Mar 1 00:36:15.743: OSPF: Interface FastEthernet0/0 going Down
*Mar 1 00:36:15.747: OSPF: 2.2.2.2 address 192.168.1.2 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:36:15.751: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.751: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.759: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.759: OSPF: Elect DR 1.1.1.1
*Mar 1 00:36:15.759: DR: 1.1.1.1 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.763: OSPF: Reset adjacency with 3.3.3.3 on FastEthernet0/0, state 2WAY
*Mar 1 00:36:15.767: OSPF: 1.1.1.1 address 192.168.1.1 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:36:15.771: %OSPF-5-ADJCHG: Process 110, Nbr 1.1.1.1 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:36:15.771: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.771: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.771: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.771: OSPF: Elect DR 4.4.4.4
*Mar 1 00:36:15.771: DR: 4.4.4.4 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.771: OSPF: Remember old DR 1.1.1.1 (id)
*Mar 1 00:36:15.771: OSPF: 3.3.3.3 address 192.168.1.3 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:36:15.771: %OSPF-5-ADJCHG: Process 110, Nbr 3.3.3.3 on FastEthernet0/0 from 2WAY to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:36:15.771: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.771: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.771: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.771: OSPF: Elect DR 4.4.4.4
*Mar 1 00:36:15.771: DR: 4.4.4.4 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.771: OSPF: 4.4.4.4 address 192.168.1.4 on FastEthernet0/0 is dead, state DOWN
*Mar 1 00:36:15.771: %OSPF-5-ADJCHG: Process 110, Nbr 4.4.4.4 on FastEthernet0/0 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar 1 00:36:15.775: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.775: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.775: OSPF: Elect BDR 0.0.0.0
*Mar 1 00:36:15.775: OSPF: Elect DR 0.0.0.0
*Mar 1 00:36:15.775: DR: none BDR: none
*Mar 1 00:36:15.775: OSPF: Remember old DR 4.4.4.4 (id)
*Mar 1 00:36:15.775: OSPF: Interface Loopback0 going Down
*Mar 1 00:36:15.775: OSPF: 2.2.2.2 address 2.2.2.2 on Loopback0 is dead, state DOWN
*Mar 1 00:36:15.787: OSPF: Interface FastEthernet0/0 going Up
*Mar 1 00:36:15.791: OSPF: Interface Loopback0 going Up
*Mar 1 00:36:15.835: OSPF: 2 Way Communication to 1.1.1.1 on FastEthernet0/0, state 2WAY
*Mar 1 00:36:15.839: OSPF: 2 Way Communication to 4.4.4.4 on FastEthernet0/0, state 2WAY
*Mar 1 00:36:15.843: OSPF: Backup seen Event before WAIT timer on FastEthernet0/0
*Mar 1 00:36:15.843: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.847: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.847: OSPF: Elect DR 1.1.1.1
*Mar 1 00:36:15.847: DR: 1.1.1.1 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.851: OSPF: Send DBD to 1.1.1.1 on FastEthernet0/0 seq 0x25DE opt 0x52 flag 0x7 len 32
*Mar 1 00:36:15.855: OSPF: Send DBD to 4.4.4.4 on FastEthernet0/0 seq 0x26D opt 0x52 flag 0x7 len 32
*Mar 1 00:36:15.863: OSPF: 2 Way Communication to 3.3.3.3 on FastEthernet0/0, state 2WAY
*Mar 1 00:36:15.863: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.867: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.867: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.871: OSPF: Elect DR 1.1.1.1
*Mar 1 00:36:15.871: DR: 1.1.1.1 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.875: OSPF: Neighbor change Event on interface FastEthernet0/0
*Mar 1 00:36:15.875: OSPF: DR/BDR election on FastEthernet0/0
*Mar 1 00:36:15.879: OSPF: Elect BDR 4.4.4.4
*Mar 1 00:36:15.879: OSPF: Elect DR 1.1.1.1
*Mar 1 00:36:15.883: DR: 1.1.1.1 (Id) BDR: 4.4.4.4 (Id)
*Mar 1 00:36:15.891: OSPF: Rcv DBD from 1.1.1.1 on FastEthernet0/0 seq 0x9D opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART
*Mar 1 00:36:15.895: OSPF: First DBD and we are not SLAVE
*Mar 1 00:36:15.895: OSPF: Rcv DBD from 1.1.1.1 on FastEthernet0/0 seq 0x25DE opt 0x52 flag 0x2 len 112 mtu 1500 state EXSTART
*Mar 1 00:36:15.899: OSPF: NBR Negotiation Done. We are the MASTER
*Mar 1 00:36:15.903: OSPF: Send DBD to 1.1.1.1 on FastEthernet0/0 seq 0x25DF opt 0x52 flag 0x1 len 32
*Mar 1 00:36:15.983: OSPF: Rcv DBD from 4.4.4.4 on FastEthernet0/0 seq 0x8FA opt 0x52 flag 0x7 len 32 mtu 1500 state EXSTART
*Mar 1 00:36:15.983: OSPF: NBR Negotiation Done. We are the SLAVE
*Mar 1 00:36:15.983: OSPF: Send DBD to 4.4.4.4 on FastEthernet0/0 seq 0x8FA opt 0x52 flag 0x0 len 32
*Mar 1 00:36:15.983: OSPF: Rcv DBD from 1.1.1.1 on FastEthernet0/0 seq 0x25DF opt 0x52 flag 0x0 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:36:15.983: OSPF: Exchange Done with 1.1.1.1 on FastEthernet0/0
*Mar 1 00:36:15.983: OSPF: Send LS REQ to 1.1.1.1 length 48 LSA count 4
*Mar 1 00:36:15.995: OSPF: Rcv LS UPD from 1.1.1.1 on FastEthernet0/0 length 212 LSA count 4
*Mar 1 00:36:16.007: OSPF: Synchronized with 1.1.1.1 on FastEthernet0/0, state FULL
*Mar 1 00:36:16.011: %OSPF-5-ADJCHG: Process 110, Nbr 1.1.1.1 on FastEthernet0/0 from LOADING to FULL, Loading Done
*Mar 1 00:36:16.019: OSPF: Rcv DBD from 4.4.4.4 on FastEthernet0/0 seq 0x8FB opt 0x52 flag 0x3 len 112 mtu 1500 state EXCHANGE
*Mar 1 00:36:16.023: OSPF: Send DBD to 4.4.4.4 on FastEthernet0/0 seq 0x8FB opt 0x52 flag 0x0 len 32
*Mar 1 00:36:16.039: OSPF: Rcv DBD from 4.4.4.4 on FastEthernet0/0 seq 0x8FC opt 0x52 flag 0x1 len 32 mtu 1500 state EXCHANGE
*Mar 1 00:36:16.039: OSPF: Exchange Done with 4.4.4.4 on FastEthernet0/0
*Mar 1 00:36:16.043: OSPF: Synchronized with 4.4.4.4 on FastEthernet0/0, state FULL
*Mar 1 00:36:16.047: %OSPF-5-ADJCHG: Process 110, Nbr 4.4.4.4 on FastEthernet0/0 from LOADING to FULL, Loading Done
*Mar 1 00:36:16.047: OSPF: Send DBD to 4.4.4.4 on FastEthernet0/0 seq 0x8FC opt 0x52 flag 0x0 len 32
*Mar 1 00:36:16.267: OSPF: Build router LSA for area 0, router ID 2.2.2.2, seq 0x80000001
*Mar 1 00:36:20.627: OSPF: Rcv LS UPD from 1.1.1.1 on FastEthernet0/0 length 76 LSA count 1
*Mar 1 00:36:20.655: OSPF: Rcv LS UPD from 4.4.4.4 on FastEthernet0/0 length 76 LSA count 1
*Mar 1 00:36:21.299: OSPF: Rcv LS UPD from 4.4.4.4 on FastEthernet0/0 length 76 LSA count 1
*Mar 1 00:36:21.323: OSPF: Rcv LS UPD from 1.1.1.1 on FastEthernet0/0 length 76 LSA count 1
*Mar 1 00:36:25.635: OSPF: Build router LSA for area 0, router ID 2.2.2.2, seq 0x80000004
*Mar 1 00:36:25.687: OSPF: Rcv LS UPD from 1.1.1.1 on FastEthernet0/0 length 76 LSA count 1
以上的输出表明：
① DR 重新选举的过程和结果，新的DR 是R1，BDR 是R4；
② 在OSPF 邻接关系建立的过程中，接口的状态的变化包括DOWN、2 Way、EXSTART、EXCHANGE、Loading 和FULL
