当在NBMA网络（如帧中继、ATM）中配置OSPF，必须注意哪个路由器是网络的DR和BDR，DR和BDR要求与网络中的所有路由器都有完全的逻辑连接。

 

同时，根据所使用的是四种网络类型中的哪一种（广播式、非广播式、点到点、点到多点），有必要使用额外的配置。

 

这个实验是在非广播的NBMA帧中继网络中使用了OSPF。这种类型是帧中继网络中物理接口的缺省类型。在非广播式网络中，存在一个DR或BDR，这要根据网络的性能，这要根据网络的性能，这个DR和BDR必须有一个包含所有处于帧中继的路由器的静态表，在OSPF进程中使用邻居命令可以完成这个任务。

 

对于这个实验，DR是路由器3，因为它具有与网络上其它所有路由器的完整的物理连接。如上图表示。

 

// 帧交换机

frame-relay switching

 

int s2/0

  encapsulation frame-relay

  clock rate 64000

  frame-relay intf-type dce

  frame-relay route 200 int s3/0 300

 

int s3/0

  encapsulation frame-relay

  clock rate 64000

  frame-relay intf-type dce

  frame-relay route 300 int s2/0 200

  frame-relay route 399 int s4/0 400

 

int s4/0

  encapsulation frame-relay

  clock rate 64000

  frame-relay intf-type dce

  frame-relay route 400 int s2/0 399

 

 

// R2 //

int s2/0

  encapsulation frame-relay

  ip ospf priority 0    //优先级为0，不参与DR选举

  ip ad 192.1.1.2 255.255.255.0

  frame-relay map ip 192.1.1.3 200 broadcast

  frame-relay map ip 192.1.1.4 200 broadcast

 

router os 1

  network 2.2.2.2 0.0.0.0 area 0

  network 192.1.1.2 0.0.0.0 area 0

 

 

// R3 //

int lo0

  ip ad 3.3.3.3 255.255.255.0

 

int s3/0

  encapsulation frame-relay

  ip address 192.1.1.3 255.255.255.0

  frame-relay map ip 192.1.1.2 300 broadcast

  frame-relay map ip 192.1.1.4 399 broadcast

 

router os 1

  network 3.3.3.3 0.0.0.0 area 0

  network 192.1.1.3 0.0.0.0 area 0

 

 

// R4 //

int lo0

  ip ad 4.4.4.4 255.255.255.0

 

int s4/0

  encapsulation frame-relay

  ip ad 192.1.1.4 255.255.255.0

  frame-relay map ip 192.1.1.2 400 broadcast

  frame-relay map ip 192.1.1.3 400 broadcast

 

router os 1

  network 4.4.4.4 0.0.0.0 area 0

  network 192.1.1.4 0.0.0.0 area 0

 

 

 

 

验证过程：

一、首先来检查DR选举是否按我们的设计，R3被选举为DR，R2、R4不参与选举，同时注意网络类型是否为NBMA，hello时间间隔是否为30秒。。。。。。

 

r3#sh ip os int s3/0
Serial3/0 is up, line protocol is up
  Internet Address 192.1.1.3/24, 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 192.1.1.3
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    Hello due in 00:00:27
  Index 2/2, 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 2, Adjacent neighbor count is 2
    Adjacent with neighbor 4.4.4.4
    Adjacent with neighbor 2.2.2.2
  Suppress hello for 0 neighbor(s)

 

 

r2#sh ip os int s2/0
Serial2/0 is up, line protocol is up
  Internet Address 192.1.1.2/24, Area 0
  Process ID 1, Router ID 2.2.2.2, Network Type NON_BROADCAST, Cost: 64
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 3.3.3.3, Interface address 192.1.1.3
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    Hello due in 00:00:20
  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
    Adjacent with neighbor 3.3.3.3  (Designated Router)
  Suppress hello for 0 neighbor(s)

 

 

r4#sh ip ospf int s4/0
Serial4/0 is up, line protocol is up
  Internet Address 192.1.1.4/24, Area 0
  Process ID 1, Router ID 4.4.4.4, Network Type NON_BROADCAST, Cost: 64
  Transmit Delay is 1 sec, State DROTHER, Priority 0
  Designated Router (ID) 3.3.3.3, Interface address 192.1.1.3
  No backup designated router on this network
  Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
    Hello due in 00:00:05
  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
    Adjacent with neighbor 3.3.3.3  (Designated Router)
  Suppress hello for 0 neighbor(s)

 

二、接下来观察各路由器邻居建立情况：

r2#sh ip os nei

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           1   FULL/DR         00:01:50    192.1.1.3       Serial2/0

 

r3#sh ip os nei

Neighbor ID     Pri   State           Dead Time   Address         Interface
4.4.4.4           0   FULL/DROTHER    00:01:41    192.1.1.4       Serial3/0
2.2.2.2           0   FULL/DROTHER    00:01:30    192.1.1.2       Serial3/0

 

r3#sh ip os nei

Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           1   FULL/DR         00:01:48    192.1.1.3       Serial4/0

 

 

三、最后验证路由：

r2#sh ip ro   

     2.0.0.0/24 is subnetted, 1 subnets
C       2.2.2.0 is directly connected, Loopback0
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/65] via 192.1.1.3, 00:00:17, Serial2/0
     4.0.0.0/32 is subnetted, 1 subnets
O       4.4.4.4 [110/65] via 192.1.1.4, 00:00:17, Serial2/0
C    192.1.1.0/24 is directly connected, Serial2/0

 

 

 

r3#sh ip ro

     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/65] via 192.1.1.2, 00:00:38, Serial3/0
     3.0.0.0/24 is subnetted, 1 subnets
C       3.3.3.0 is directly connected, Loopback0
     4.0.0.0/32 is subnetted, 1 subnets
O       4.4.4.4 [110/65] via 192.1.1.4, 00:00:38, Serial3/0
C    192.1.1.0/24 is directly connected, Serial3/0

 

 

 

r4#sh ip ro

     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/65] via 192.1.1.2, 00:01:04, Serial4/0
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/65] via 192.1.1.3, 00:01:04, Serial4/0
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback0
C    192.1.1.0/24 is directly connected, Serial4/0
r4#