在NBMA网络广播模式下配置OSPF实际案例（配图）＋详细验证过程

广播式网络是一个渐进的操作过程,它可以定义所有邻居。当给一个接口配置广播时，这个接口就好像是连入了LAN中，网络中仍要选出DR和BDR，需特别保证路由器选出的DR/BDR与网络中所有路由器都有物理连接。

使用接口命令ip ospf network broadcast可以向所有路由器上设置网络类型。R2、R4的串行接口被配置成OSPF PRIORITY为0，这将保证R3成为DR。

// 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 ospf network broadcast //将OSPF网络类型设置为广播模式
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 ospf network broadcast //将OSPF网络类型设置为广播模式
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
ip ospf network broadcast //将OSPF网络类型设置为广播模式
ip ospf priority 0 //优先级为0，不参与DR选举
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 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 10, Dead 40, Wait 40, 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 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 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:06
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 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 10, Dead 40, Wait 40, 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#

如果我们将R2路由器的优先级调整为10，重启后R2将成为DR，R3作为BDR，R4作为DROTHER，这样的结果会导致R4无法收到R2、R3的路由更新，原因如下：

r4#sh ip ospf database
OSPF Router with ID (4.4.4.4) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
2.2.2.2 2.2.2.2 99 0x80000009 0xCF69 2
3.3.3.3 3.3.3.3 109 0x8000000B 0xDF4A 2
4.4.4.4 4.4.4.4 107 0x8000000C 0xFB1F 2
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
192.1.1.2 2.2.2.2 108 0x80000001 0x4910

r4#sh ip os database router
OSPF Router with ID (4.4.4.4) (Process ID 1)
Router Link States (Area 0)
Adv Router is not-reachable
LS age: 124
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 2.2.2.2
Advertising Router: 2.2.2.2
LS Seq Number: 80000009
Checksum: 0xCF69
Length: 48
Number of Links: 2
Link connected to: a Transit Network
(Link ID) Designated Router address: 192.1.1.2
(Link Data) Router Interface address: 192.1.1.2
Number of TOS metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 2.2.2.2
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metrics: 1

Adv Router is not-reachable
LS age: 198
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 3.3.3.3
Advertising Router: 3.3.3.3
LS Seq Number: 8000000B
Checksum: 0xDF4A
Length: 48
Number of Links: 2
Link connected to: a Transit Network
(Link ID) Designated Router address: 192.1.1.2
(Link Data) Router Interface address: 192.1.1.3
Number of TOS metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 3.3.3.3
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metrics: 1

LS age: 215
Options: (No TOS-capability, DC)
LS Type: Router Links
Link State ID: 4.4.4.4
Advertising Router: 4.4.4.4
LS Seq Number: 8000000C
Checksum: 0xFB1F
Length: 48
Number of Links: 2
Link connected to: a Transit Network
(Link ID) Designated Router address: 192.1.1.3
(Link Data) Router Interface address: 192.1.1.4
Number of TOS metrics: 0
TOS 0 Metrics: 64
Link connected to: a Stub Network
(Link ID) Network/subnet number: 4.4.4.4
(Link Data) Network Mask: 255.255.255.255
Number of TOS metrics: 0
TOS 0 Metrics: 1