一个点到多点网络被看作若干具有一个或多个邻居的点到点接口。当一个接口被配置给点到多点网络，就不需要DR/BDR，不需要定义邻居，这大大简化了给NBMA网络配置OSPF。
 
使用端口命令 ip ospa network point-to-multioint可以给所有路由器设置网络类型。既不需要定义邻居，也不需要设置优先级，因为网络中没有DR/BDR。
 
// 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 lo0
  ip ad 2.2.2.2 255.255.255.0
 
int s2/0
  encapsulation frame-relay
  ip ad 192.1.1.2 255.255.255.0
  ip ospf network point-to-multipoint    //改变接口模式为点到多点
  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
  ip ospf network point-to-multipoint    //改变接口模式为点到多点
  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
  ip ospf network point-to-multipoint    //改变接口模式为点到多点
  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
 
注意上述配置中没有任何特别操作，比如使用neighbor命令指明邻居，设置OSPF优先级等等，这就是点到多点模式下的特点。
 
 
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 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 2/2, 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 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 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 00:00:01
  Index 2/2, 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 0 msec
  Neighbor Count is 1, Adjacent neighbor count is 1
    Adjacent with neighbor 3.3.3.3
  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 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 00:00:02
  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
  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/  -        00:01:33    192.1.1.3       Serial2/0
 
r3#sh ip os nei
Neighbor ID     Pri   State           Dead Time   Address         Interface
4.4.4.4           1   FULL/  -        00:01:56    192.1.1.4       Serial3/0
2.2.2.2           1   FULL/  -        00:01:36    192.1.1.2       Serial3/0
 
r4#sh ip os nei
Neighbor ID     Pri   State           Dead Time   Address         Interface
3.3.3.3           1   FULL/  -        00:01:37    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, 00:08:30, Serial2/0
     4.0.0.0/32 is subnetted, 1 subnets
O       4.4.4.4 [110/129] via 192.1.1.3, 00:08:30, Serial2/0
     192.1.1.0/24 is variably subnetted, 3 subnets, 2 masks
C       192.1.1.0/24 is directly connected, Serial2/0
O       192.1.1.3/32 [110/64] via 192.1.1.3, 00:08:30, Serial2/0
O       192.1.1.4/32 [110/128] via 192.1.1.3, 00:08:30, 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, 00:08:54, 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, 00:08:54, Serial3/0
     192.1.1.0/24 is variably subnetted, 3 subnets, 2 masks
C       192.1.1.0/24 is directly connected, Serial3/0
O       192.1.1.2/32 [110/64] via 192.1.1.2, 00:08:54, Serial3/0
O       192.1.1.4/32 [110/64] via 192.1.1.4, 00:08:54, Serial3/0
 
 
 
r4#sh ip ro
     2.0.0.0/32 is subnetted, 1 subnets
O       2.2.2.2 [110/129] via 192.1.1.3, 00:09:20, Serial4/0
     3.0.0.0/32 is subnetted, 1 subnets
O       3.3.3.3 [110/65] via 192.1.1.3, 00:09:20, Serial4/0
     4.0.0.0/24 is subnetted, 1 subnets
C       4.4.4.0 is directly connected, Loopback0
     192.1.1.0/24 is variably subnetted, 3 subnets, 2 masks
C       192.1.1.0/24 is directly connected, Serial4/0
O       192.1.1.2/32 [110/128] via 192.1.1.3, 00:09:20, Serial4/0
O       192.1.1.3/32 [110/64] via 192.1.1.3, 00:09:20, Serial4/0
 
 
注意，在点到多点或点到点模式下，路由表中会自动生成32位主机路由。