HCNA-34 OSPF的DR与BDR

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HCNA-34 OSPF的DR与BDR

标注：DR/Designated Router 指定路由；BDR/BackupDesignated Router 备份指定路由；NBMA/Non-Broadcast MultipleAccess 非广播多路访问；邻接关系公式n*(n-1)/2；

OSPF链路分为3种：1、广播（broadcast）2、NBMA 3、点到点（point-to-point）再扩展出5种类型：1、广播 2、NBMA 3、点到点4、点到多点（point-to-multipoint） 5、虚链路

<Huawei>system-view

[Huawei]sysnamer1

[r1]interfaceloopback 0  //创建环回口 0

[r1-LoopBack0]ipaddress 1.1.1.1 32

[r1-LoopBack0]interfaceGigabitEthernet 0/0/0

[r1-GigabitEthernet0/0/0]ipaddress 172.16.100.1 24

[r1-GigabitEthernet0/0/0]

[r1-GigabitEthernet0/0/0]quit

[r1]routerid 1.1.1.1  //配置全局路由ID

[r1]ospf1  //创建OSPF 进程1

[r1-ospf-1]area0  //创建骨干区域 0

[r1-ospf-1-area-0.0.0.0]network1.1.1.1 0.0.0.0  //通告参考网络 地址段+通配符掩码

[r1-ospf-1-area-0.0.0.0]network172.16.100.0 0.0.0.255

[r1-ospf-1-area-0.0.0.0]authentication-modemd5 1 cipher admin1234  //配置身份认证模式为MD5 密文加加密

[r1-ospf-1-area-0.0.0.0]return

<Huawei>system-view

[Huawei]sysnamer2

[r2]interfaceloopback 0

[r2-LoopBack0]ipaddress 2.2.2.2 32

[r2-LoopBack0]interfaceGigabitEthernet 0/0/0

[r2-GigabitEthernet0/0/0]ipaddress 172.16.100.2 24

[r2-GigabitEthernet0/0/0]quit

[r2]routerid 2.2.2.2

[r2]ospf1

[r2-ospf-1]area0

[r2-ospf-1-area-0.0.0.0]network2.2.2.2 0.0.0.0

[r2-ospf-1-area-0.0.0.0]network172.16.100.0 0.0.0.255

[r2-ospf-1-area-0.0.0.0]authentication-modemd5 1 cipher admin1234

[r2-ospf-1-area-0.0.0.0]return

<Huawei>system-view

[Huawei]sysnamer3

[r3]interfaceloopback 0

[r3-LoopBack0]ipaddress 3.3.3.3 32

[r3-LoopBack0]interfaceGigabitEthernet 0/0/0

[r3-GigabitEthernet0/0/0]ipaddress 172.16.100.3 24

[r3-GigabitEthernet0/0/0]quit

[r3]routerid 3.3.3.3

[r3]ospf1

[r3-ospf-1]area0

[r3-ospf-1-area-0.0.0.0]network3.3.3.3 0.0.0.0

[r3-ospf-1-area-0.0.0.0]network172.16.100.0 0.0.0.255

[r3-ospf-1-area-0.0.0.0]authentication-modemd5 1 cipher admin1234

[r3-ospf-1-area-0.0.0.0]

[r3-ospf-1-area-0.0.0.0]return

<Huawei>system-view

[Huawei]sysnamer4

[r4]interfaceloopback 0

[r4-LoopBack0]ipaddress 4.4.4.4 32

[r4-LoopBack0]interfaceGigabitEthernet 0/0/0

[r4-GigabitEthernet0/0/0]ipaddress 172.16.100.4 24

[r4-GigabitEthernet0/0/0]quit

[r4]routerid 4.4.4.4

[r4]ospf1

[r4-ospf-1]area0

[r4-ospf-1-area-0.0.0.0]network4.4.4.4 0.0.0.0

[r4-ospf-1-area-0.0.0.0]network172.16.100.0 0.0.0.255

[r4-ospf-1-area-0.0.0.0]authentication-modemd5 1 cipher admin1234

[r4-ospf-1-area-0.0.0.0]return

配置完成后，同步重启四台路由，让OSPF重新进行计算，选举出DR，BDR

<r1>displayospf peer brief  //查看OSPF邻居简要信息

        OSPF Process 1 with Router ID 1.1.1.1

               Peer Statistic Information  

----------------------------------------------------------------------------

Area Id          Interface                        Neighbor id      State   

0.0.0.0          GigabitEthernet0/0/0             2.2.2.2          Full        

0.0.0.0          GigabitEthernet0/0/0             3.3.3.3          Full        

0.0.0.0          GigabitEthernet0/0/0             4.4.4.4          Full      

----------------------------------------------------------------------------

4组路由器已经成功建立起邻居关系。

下面验证一下默认情况下DR和BDR状态

<r1>displayospf peer  //查看OSPF邻居状态

        OSPF Process 1 with Router ID 1.1.1.1

               Neighbors

Area 0.0.0.0 interface172.16.100.1(GigabitEthernet0/0/0)'s neighbors

Router ID: 2.2.2.2          Address: 172.16.100.2   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: 172.16.100.3  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 33  sec

   Retrans timer interval: 4

   Neighbor is up for 00:17:06     

   Authentication Sequence: [ 76]

Router ID: 3.3.3.3          Address: 172.16.100.3   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: 172.16.100.3  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 34  sec

   Retrans timer interval: 5

   Neighbor is up for 00:17:04     

   Authentication Sequence: [ 80]

Router ID: 4.4.4.4          Address: 172.16.100.4   

   State: 2-Way Mode:Nbr is  Master  Priority: 1

   DR: 172.16.100.3  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 37  sec

   Retrans timer interval: 0

   Neighbor is up for 00:00:00     

   Authentication Sequence: [ 0 ]

分析得出：R3是DR，R2是BDR；在默认情况下每台路由器上的DR优先级都是1，此时是通过Router-ID的数值高低来进行比较的，数值大的会成为DR,次之百为BDR；那么在目前这个情况，为何DR是R3，BDR是R2，这个是根据路由器的配置或启动序列排列的，可以认为谁先配置谁成为DR,谁先启动，谁成为DR。

下面配置每台设备上的相关接口下使用ospf network-type p2mp命令修改OSPF的网络类型为点到多点。

[r1]interfaceGigabitEthernet 0/0/0

[r1-GigabitEthernet0/0/0]ospfnetwork-type p2mp

[r2]interfaceGigabitEthernet 0/0/0

[r2-GigabitEthernet0/0/0]ospfnetwork-type p2mp

[r3]interfaceGigabitEthernet 0/0/0

[r3-GigabitEthernet0/0/0]ospfnetwork-type p2mp

[r4]interfaceGigabitEthernet 0/0/0

[r4-GigabitEthernet0/0/0]ospfnetwork-type p2mp

[r1]displayospf peer

        OSPF Process 1 with Router ID 1.1.1.1

               Neighbors

Area 0.0.0.0 interface172.16.100.1(GigabitEthernet0/0/0)'s neighbors

Router ID: 2.2.2.2          Address: 172.16.100.2   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: None   BDR: None   MTU: 0   

   Dead timer due in 93  sec

   Retrans timer interval: 5

   Neighbor is up for 00:04:12     

   Authentication Sequence: [ 585]

Router ID: 3.3.3.3          Address: 172.16.100.3   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: None   BDR: None   MTU: 0   

   Dead timer due in 113 sec

   Retrans timer interval: 5

   Neighbor is up for 00:03:44     

   Authentication Sequence: [ 580]

Router ID: 4.4.4.4          Address: 172.16.100.4   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: None   BDR: None   MTU: 0   

   Dead timer due in 90  sec

   Retrans timer interval: 5

   Neighbor is up for 00:02:46     

   Authentication Sequence: [ 576]

分析得出，DR和BDR全部为None，说明了一点，在OSPF点多到点和点到点网络中，不存在DR与BDR的选举。

下面根据拓扑要求配置影响DR/BDR选举：

R1为DR（性能最好）；R2为BDR（性能次之）；R4不参选（因为性能最差）；R3成为DR Other

[r1]interfaceGigabitEthernet 0/0/0

[r1-GigabitEthernet0/0/0]ospfnetwork-type broadcast  //配置OSPF网络类型为广播网络

[r2]interfaceGigabitEthernet 0/0/0

[r2-GigabitEthernet0/0/0]ospfnetwork-type broadcast

[r3]interfaceGigabitEthernet 0/0/0

[r3-GigabitEthernet0/0/0]ospfnetwork-type broadcast

[r4]interfaceGigabitEthernet 0/0/0

[r4-GigabitEthernet0/0/0]ospfnetwork-type broadcast

[r1]interfaceGigabitEthernet 0/0/0

[r1-GigabitEthernet0/0/0]ospfdr-priority 100  //配置OSPF DR优先级为100

[r2]interfaceGigabitEthernet 0/0/0

[r2-GigabitEthernet0/0/0]ospfdr-priority 50

[r4]interfaceGigabitEthernet 0/0/0

[r4-GigabitEthernet0/0/0]ospfdr-priority 0

验证DR/BDR

<r1>displayospf peer

        OSPF Process 1 with Router ID 1.1.1.1

               Neighbors

Area 0.0.0.0 interface172.16.100.1(GigabitEthernet0/0/0)'s neighbors

Router ID: 2.2.2.2          Address: 172.16.100.2   

   State: Full Mode:Nbr is  Master  Priority: 50

   DR: 172.16.100.1  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 39  sec

   Retrans timer interval: 5

   Neighbor is up for 00:17:00     

   Authentication Sequence: [ 2095]

Router ID: 3.3.3.3          Address: 172.16.100.3   

   State: Full Mode:Nbr is  Master  Priority: 1

   DR: 172.16.100.1  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 31  sec

   Retrans timer interval: 5

   Neighbor is up for 00:14:48     

   Authentication Sequence: [ 2090]

Router ID: 4.4.4.4          Address: 172.16.100.4   

   State: Full Mode:Nbr is  Master  Priority: 0

   DR: 172.16.100.1  BDR:172.16.100.2  MTU: 0   

   Dead timer due in 37  sec

   Retrans timer interval: 5

   Neighbor is up for 00:01:41     

   Authentication Sequence: [ 2087]

此时网络实现了拓扑要求。

说明：ospf dr-priority 优先级越高，越会成为DR，次之成为BDR，优先级为0则代表不参与选举。

<r3>displayospf brief

        OSPF Process 1 with Router ID 3.3.3.3

               OSPF Protocol Information

RouterID: 3.3.3.3          Border Router:

……

Area: 0.0.0.0          (MPLS TE not enabled)

Authtype: MD5  Area flag: Normal

SPF scheduled Count: 53   

ExChange/Loading Neighbors: 0

Router ID conflict state: Normal

Area interface up count: 2

Interface: 172.16.100.3 (GigabitEthernet0/0/0)

Cost: 1      State: DROther    Type: Broadcast    MTU: 1500

Priority: 1

Designated Router: 172.16.100.1

Backup Designated Router: 172.16.100.2

Timers: Hello 10 , Dead 40 , Poll  120 , Retransmit 5 , Transmit Delay 1

Interface: 3.3.3.3 (LoopBack0)

Cost: 0      State: P-2-P     Type: P2P       MTU: 1500  

Timers: Hello 10 , Dead 40 , Poll  120 , Retransmit 5 , Transmit Delay 1

R3也自然成为了DR Other。

测试网络：

<r1>ping-a 1.1.1.1 2.2.2.2

  PING 2.2.2.2: 56  data bytes, press CTRL_C to break

    Reply from 2.2.2.2: bytes=56 Sequence=1ttl=255 time=170 ms

    Reply from 2.2.2.2: bytes=56 Sequence=2ttl=255 time=40 ms

    Reply from 2.2.2.2: bytes=56 Sequence=3ttl=255 time=40 ms

    Reply from 2.2.2.2: bytes=56 Sequence=4ttl=255 time=50 ms

    Replyfrom 2.2.2.2: bytes=56 Sequence=5 ttl=255 time=50 ms

  --- 2.2.2.2 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 40/70/170 ms

<r1>ping-a 1.1.1.1 3.3.3.3

  PING 3.3.3.3: 56  data bytes, press CTRL_C to break

    Reply from 3.3.3.3: bytes=56 Sequence=1ttl=255 time=70 ms

    Reply from 3.3.3.3: bytes=56 Sequence=2ttl=255 time=40 ms

    Reply from 3.3.3.3: bytes=56 Sequence=3ttl=255 time=40 ms

    Reply from 3.3.3.3: bytes=56 Sequence=4ttl=255 time=40 ms

    Reply from 3.3.3.3: bytes=56 Sequence=5ttl=255 time=50 ms

  --- 3.3.3.3 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 40/48/70 ms

<r1>ping-a 1.1.1.1 4.4.4.4

  PING 4.4.4.4: 56  data bytes, press CTRL_C to break

    Reply from 4.4.4.4: bytes=56 Sequence=1ttl=255 time=100 ms

    Reply from 4.4.4.4: bytes=56 Sequence=2ttl=255 time=50 ms

    Reply from 4.4.4.4: bytes=56 Sequence=3ttl=255 time=50 ms

    Reply from 4.4.4.4: bytes=56 Sequence=4ttl=255 time=50 ms

    Reply from 4.4.4.4: bytes=56 Sequence=5ttl=255 time=50 ms

  --- 4.4.4.4 ping statistics ---

    5 packet(s) transmitted

    5 packet(s) received

    0.00% packet loss

    round-trip min/avg/max = 50/60/100 ms