基于非广播型链路的 OSPF 的初始配置

简介

本文为在非广播链路的开放最短路径优先(OSPF)提供初始配置。在非广播介质（例如，帧中继、X.25、ATM 和交换式多兆位数据服务 (SMDS)）上，OSPF 可以在两种模式下运行：

• 非广播多路访问(NBMA) ：由指定路由器(DR)和备份指定路由器模拟广播模型(BDR)的选择。在 NBMA 网络上模拟广播模型的方式有两种：使用 ip ospf network broadcast 接口子命令将网络类型定义为广播，或者使用 router ospf 命令配置邻居语句。

• 单点对多点：对待非广播网络作为点对点链路的一集由配置ip ospf network point-to-multipoint命令。

您必须定义在非广播网络的网络类型为了避免邻居语句的配置。本文为在非广播链路的OSPF提供配置示例。请使用show ip ospf interface命令为了检查运行OSPF，并且show ip ospf neighbor命令用于认识邻接路由器的状态接口的网络类型。

先决条件

要求

思科建议您了解OSPF路由协议的基本配置。

使用的组件

本文档中的信息基于以下软件和硬件版本：

• Cisco 2500 路由器

• 在路由器运行的Cisco IOS软件版本12.2(24a)

本文档中的信息都是基于特定实验室环境中的设备创建的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您使用的是真实网络，请确保您已经了解所有命令的潜在影响。

网络图

这是用于在本文的配置示例的网络图。

NBMA的(使用网络类型广播)配置

interface Loopback0
      ip address 3.3.3.3 255.255.255.255
     !
     !
     interface Serial2
      ip address 1.1.1.2 255.255.255.0
      encapsulation frame-relay
      ip ospf network broadcast
      no keepalive
      frame-relay map ip 1.1.1.1 16 broadcast
     !
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0

interface Loopback0
      ip address 2.2.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 1.1.1.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network broadcast
      no keepalive
      clockrate 2000000
      frame-relay map ip 1.1.1.2 16 broadcast
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0
     !

验证提示

这是Router1的show命令输出。

Router1# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     2.2.2.2           1   FULL/BDR        00:00:37    1.1.1.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 1.1.1.2/24, Area 0 
       Process ID 1, Router ID 3.3.3.3, Network Type BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State DR, Priority 1 
       Designated Router (ID) 3.3.3.3, Interface address 1.1.1.2
       Backup Designated router (ID) 2.2.2.2, Interface address 1.1.1.1
       Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
         Hello due in 00:00:00
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 1, maximum is 2
       Last flood scan time is 0 msec, maximum is 4 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 2.2.2.2  (Backup Designated Router)
       Suppress hello for 0 neighbor(s)

Router2 的输出如下所示。

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     3.3.3.3           1   FULL/DR         00:00:38     1.1.1.2         Serial1/0
     
Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 1.1.1.1/24, Area 0 
       Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State BDR, Priority 1 
       Designated Router (ID) 3.3.3.3, Interface address 1.1.1.2
       Backup Designated router (ID) 2.2.2.2, Interface address 1.1.1.1
       Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
         Hello due in 00:00:03
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 1, maximum is 2
       Last flood scan time is 0 msec, maximum is 4 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 3.3.3.3  (Designated Router)
       Suppress hello for 0 neighbor(s)

NBMA的(使用邻居语句)配置

interface Loopback0
      ip address 3.3.3.3 255.255.255.255
     !
     interface Serial2
      ip address 1.1.1.2 255.255.255.0
      encapsulation frame-relay
      ip ospf priority 2
      no keepalive
      frame-relay map ip 1.1.1.1 16
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0
      neighbor 1.1.1.1
     !

interface Loopback0
      ip address 2.2.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 1.1.1.1 255.255.255.0
      encapsulation frame-relay
      no keepalive
      clockrate 2000000
      frame-relay map ip 1.1.1.2 16
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0
      neighbor 1.1.1.2
     !

注意： 在显示的配置中， ip ospf priority 2命令在Router1比默认优先级值设置一个接口优先级为1，做它DR和Router2 NBMA网络的BDR。若需要，您不能设置优先级值到0为了配置路由器变为DR/BDR。这在星型网络中是必要的，在该网络中应该将集线器配置为 DR，分支既不应该是 DR 也不应该是 BDR。虽则邻居语句的配置在一端的是满足形成邻接，它是良好的做法安排它配置在两个末端如显示。并且，因为 OSPF 数据包是使用 neighbor 语句进行单播的，所以 frame-relay map 命令不需要包含 broadcast 参数。

验证提示

这是Router1的show命令输出。

Router1# show ip ospf neighbors
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     2.2.2.2           1   FULL/BDR        00:01:39    1.1.1.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 1.1.1.2/24, Area 0 
       Process ID 1, Router ID 3.3.3.3, Network Type NON_BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State DR, Priority 1 
       Designated Router (ID) 3.3.3.3, Interface address 1.1.1.2
       Backup Designated router (ID) 2.2.2.2, Interface address 1.1.1.1
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:19
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 2, maximum is 2
       Last flood scan time is 0 msec, maximum is 0 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 2.2.2.2  (Backup Designated Router)
       Suppress hello for 0 neighbor(s)

Router2 的输出如下所示。

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     3.3.3.3           1   FULL/DR         00:01:49     1.1.1.2         Serial1/0
     
Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 1.1.1.1/24, Area 0 
       Process ID 1, Router ID 2.2.2.2, Network Type NON_BROADCAST, Cost: 64
       Transmit Delay is 1 sec, State BDR, Priority 1 
       Designated Router (ID) 3.3.3.3, Interface address 1.1.1.2
       Backup Designated router (ID) 2.2.2.2, Interface address 1.1.1.1
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:01
       Index 1/1, flood queue length 0
       Next 0x0(0)/0x0(0)
       Last flood scan length is 2, maximum is 2
       Last flood scan time is 0 msec, maximum is 0 msec
       Neighbor Count is 1, Adjacent neighbor count is 1 
         Adjacent with neighbor 3.3.3.3  (Designated Router)
       Suppress hello for 0 neighbor(s)

点对多点的配置

interface Loopback0
      ip address 3.3.3.3 255.255.255.255
     !
     interface Serial2
      ip address 1.1.1.2 255.255.255.0
      encapsulation frame-relay
      ip ospf network point-to-multipoint
      no keepalive
      frame-relay map ip 1.1.1.1 16 broadcast
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0
     !

interface Loopback0
      ip address 2.2.2.2 255.255.255.255
     !
     interface Serial1/0
      ip address 1.1.1.1 255.255.255.0
      encapsulation frame-relay
      ip ospf network point-to-multipoint
      no keepalive
      clockrate 2000000
      frame-relay map ip 1.1.1.2 16 broadcast
     !
     router ospf 1
      network 1.1.1.0 0.0.0.255 area 0

验证提示

这是Router1的show命令输出。

Router1# show ip ospf neighbors
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     2.2.2.2           1   FULL/  -        00:01:53    1.1.1.1         Serial2
     
Router1# show ip ospf interface s2
     Serial2 is up, line protocol is up 
       Internet Address 1.1.1.2/24, Area 0 
       Process ID 1, Router ID 3.3.3.3, Network Type POINT_TO_MULTIPOINT, Cost: 64
       Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:18
       Index 1/1, 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 
         Adjacent with neighbor 2.2.2.2
       Suppress hello for 0 neighbor(s)

Router2 的输出如下所示。

Router2# show ip ospf neighbor
      
     Neighbor ID     Pri   State           Dead Time   Address         Interface
     3.3.3.3           1   FULL/  -        00:01:58     1.1.1.2         Serial1/0

Router2# show ip ospf interface s1/0
     Serial1/0 is up, line protocol is up 
       Internet Address 1.1.1.1/24, Area 0 
       Process ID 1, Router ID 2.2.2.2, Network Type POINT_TO_MULTIPOINT, Cost: 64
       Transmit Delay is 1 sec, State POINT_TO_MULTIPOINT,
       Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
         Hello due in 00:00:18
       Index 1/1, 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 
         Adjacent with neighbor 3.3.3.3
       Suppress hello for 0 neighbor(s)

注意：如输出所示，将 NBMA 网络配置为单点对多点时，没有选择任何 DR 和 BDR，因为会将该网络视为点对点链路的集合。

欲知更多信息，请参阅配置OSPF。

相关信息

• OSPF 支持页
• IP路由协议支持页
• 技术支持和文档 - Cisco Systems