使用广播模式可以避免静态地列出所有的邻接路由器。接口被设置为Broadcast模式后，其行为就像LAN一样，将选举DR和BDR。因此，需确保使用全互联或部分互联拓扑，或者根据接口优先级静态地选择DR。
    Router(config)#interface serial 0/0/0
    Router(config-if)#encapsulation frame-relay
    Router(config-if)#ip ospf network broadcast
     
     
    实验：
    采用全互联拓扑，R1，R2，R3上分别设置Lo0，ip地址分别为1.1.1.1 2.2.2.2   3.3.3.3 ，默认情况下，R3将成为DR。手工指定R1为DR，且R2和R3不参与选举，设置其接口优先级为0。
     
     

    NBMA网络OSPF Broadcast类型_OSPF

     
    配置：
    FR：
    frame-relay switching
     
    int s0/0
    no ip add
    no sh
    bandwidth xxxx    
    encapsulation frame-relay
    frame-relay lmi-type cisco
    frame-relay intf-type dce
    clockrate 56000 ！
    frame-relay route 102 int s0/1 201
    frame-relay route 103 int s0/2 301  
     
    int s0/1
    no ip add
    no sh
    encapsulation frame-relay
    frame-relay intf-type dce
    clockrate 56000
    frame-relay route 201 int s0/0 102
    frame-relay route 203 int s0/2 302
     
    int s0/2
    no ip add
    no sh
    encapsulation frame-relay
    frame-relay intf-type dce
    clockrate 56000
    frame-relay route 301 int s0/0 103
    frame-relay route 302 int s0/1 203
     
    R1:
    interface Serial0/0
     ip address 192.168.1.1 255.255.255.0
     encapsulation frame-relay
     serial restart-delay 0
     frame-relay map ip 192.168.1.1 102 broadcast
     frame-relay map ip 192.168.1.2 102 broadcast 
     frame-relay map ip 192.168.1.3 103 broadcast 
     ip ospf priority 255             //指定接口优先级为255，使之成为DR
     ip ospf network broadcast                                          //指定OSPF网络类型为Broadcast
     
     
    router ospf 1
     router-id 1.1.1.1
     log-adjacency-changes
     network 1.1.1.0 0.0.0.255 area 0
     network 192.168.1.0 0.0.0.255 area 0
     
     
    R2：（接口配置）
    interface Serial0/1
     ip address 192.168.1.2 255.255.255.0
     encapsulation frame-relay
     ip ospf network broadcast
     ip ospf priority 0
     serial restart-delay 0
     frame-relay map ip 192.168.1.1 201 broadcast
     frame-relay map ip 192.168.1.2 201 broadcast
     frame-relay map ip 192.168.1.3 203 broadcast
     
     
    R3：（接口配置）
    interface Serial0/2
     ip address 192.168.1.3 255.255.255.0
     encapsulation frame-relay
     ip ospf network broadcast
     ip ospf priority 0
     serial restart-delay 0
     frame-relay map ip 192.168.1.1 301 broadcast
     frame-relay map ip 192.168.1.2 302 broadcast
     frame-relay map ip 192.169.1.3 301 broadcast
     
     
     
    验证：
    R1#sh ip ospf int s0/0
    Serial0/0 is up, line protocol is up
     Internet Address 192.168.1.1/24, Area 0
     Process ID 1, Router ID 1.1.1.1, Network Type BROADCAST, Cost: 64
     Transmit Delay is 1 sec, State DR, Priority 255
     Designated Router (ID) 1.1.1.1, Interface address 192.168.1.1
     No backup designated router on this network
     Old designated Router (ID) 3.3.3.3, Interface address 192.168.1.3
     Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
        oob-resync timeout 40
        Hello due in 00:00:03
     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 4 msec, maximum is 4 msec
     Neighbor Count is 2, Adjacent neighbor count is 2
       Adjacent with neighbor 2.2.2.2
        Adjacent with neighbor 3.3.3.3
     Suppress hello for 0 neighbor(s)
     
     

    R1#sh ip ospf nei

    Neighbor ID     Pri   State           Dead Time   Address         Interface
    2.2.2.2           0   FULL/DROTHER    00:00:39    192.168.1.2     Serial0/0
    3.3.3.3           0   FULL/DROTHER    00:00:30    192.168.1.3     Serial0/0
     
     
    R1#sh ip ro os
         2.0.0.0/24 is subnetted, 1 subnets
    O       2.2.2.0 [110/65] via 192.168.1.2, 00:00:05, Serial0/0
         3.0.0.0/24 is subnetted, 1 subnets
    O       3.3.3.0 [110/65] via 192.168.1.3, 00:00:05, Serial0/0