OSPF点到点模式，点到点子接口具有点到点物理接口的特性，没有DR/BDR，不需要配置邻居，默认情况下，OSPF在点到点子接口上使用point-to-point模式。
配置子接口，两种模式：point-to-point和point-to-multipoint：
point-to-point：
point-to-multipoint：默认使用non-broadcast OSPF模式。
实验：
配置：
FR：
no ip routing
frame-relay switching
interface Serial0/0
no ip address
encapsulation frame-relay
no ip route-cache
serial restart-delay 0
clock rate 56000
frame-relay lmi-type cisco
frame-relay intf-type dce
frame-relay route 102 interface Serial0/1 201
frame-relay route 103 interface Serial0/2 301
!
interface Serial0/1
no ip address
encapsulation frame-relay
no ip route-cache
serial restart-delay 0
clock rate 56000
frame-relay lmi-type cisco
frame-relay intf-type dce
frame-relay route 201 interface Serial0/0 102
!
interface Serial0/2
no ip address
encapsulation frame-relay
no ip route-cache
serial restart-delay 0
clock rate 56000
frame-relay lmi-type cisco
frame-relay intf-type dce
frame-relay route 301 interface Serial0/0 103
R1：
interface Loopback0
ip address 1.1.1.1 255.255.255.0
ip ospf network point-to-point
!
interface Serial0/0
no ip address
encapsulation frame-relay
serial restart-delay 0
!
interface Serial0/0.12 point-to-point
ip address 12.12.12.1 255.255.255.0
frame-relay interface-dlci 102
!
interface Serial0/0.13 point-to-point
ip address 13.13.13.1 255.255.255.0
frame-relay interface-dlci 103
router ospf 100
router-id 1.1.1.1
log-adjacency-changes
network 1.1.1.0 0.0.0.255 area 0
network 12.12.12.0 0.0.0.255 area 0
network 13.13.13.0 0.0.0.255 area 0
R2：
interface Loopback0
ip address 2.2.2.2 255.255.255.0
ip ospf network point-to-point
!
interface Serial0/0
ip address 12.12.12.2 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-point
serial restart-delay 0
frame-relay interface-dlci 201
router ospf 100
router-id 2.2.2.2
log-adjacency-changes
network 2.2.2.0 0.0.0.255 area 0
network 12.12.12.0 0.0.0.255 area 0
!
R3：
interface Loopback0
ip address 3.3.3.3 255.255.255.0
ip ospf network point-to-point
!
interface Serial0/0
ip address 13.13.13.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-point
serial restart-delay 0
frame-relay interface-dlci 301
router ospf 100
router-id 3.3.3.3
log-adjacency-changes
network 3.3.3.0 0.0.0.255 area 0
network 13.13.13.0 0.0.0.255 area 0
分别查看R1 R2 R3三台路由器上和FR相连的接口配置：
R1：
R1#sh run int s0/0
Building configuration...
Current configuration : 93 bytes
!
interface Serial0/0
no ip address
encapsulation frame-relay
serial restart-delay 0
end
R1#sh run int s0/0.12
Building configuration...
Current configuration : 117 bytes
!
interface Serial0/0.12 point-to-point //定义点到点子接口，
ip address 12.12.12.1 255.255.255.0
frame-relay interface-dlci 102 //采用了动态学习帧中继路由。
end
R1#sh run int s0/0.13
Building configuration...
Current configuration : 117 bytes
!
interface Serial0/0.13 point-to-point
ip address 13.13.13.1 255.255.255.0
frame-relay interface-dlci 103
end
R2：
R2#sh run int s0/0
Building configuration...
Current configuration : 179 bytes
!
interface Serial0/0
ip address 12.12.12.2 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-point //定义ospf模式为point-to-point，默认为Non-Broadcast。
serial restart-delay 0
frame-relay interface-dlci 201
R3：
R3#sh run int s0/0
Building configuration...
Current configuration : 179 bytes
!
interface Serial0/0
ip address 13.13.13.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-point
serial restart-delay 0
frame-relay interface-dlci 301
end
查看R1上的OSPF邻居信息：
R1#sh ip ospf nei
Neighbor ID Pri State Dead Time Address Interface
3.3.3.3 0 FULL/ - 00:00:33 13.13.13.3 Serial0/0.13
2.2.2.2 0 FULL/ - 00:00:38 12.12.12.2 Serial0/0.12
邻居自动学习得到，没有选举DR/BDR
查看路由信息：
R1#sh ip ro ospf
2.0.0.0/24 is subnetted, 1 subnets
O 2.2.2.0 [110/65] via 12.12.12.2, 00:24:44, Serial0/0.12
3.0.0.0/24 is subnetted, 1 subnets
O 3.3.3.0 [110/65] via 13.13.13.3, 00:24:44, Serial0/0.13
R2#sh ip ro os
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/65] via 12.12.12.1, 00:25:16, Serial0/0
3.0.0.0/24 is subnetted, 1 subnets
O 3.3.3.0 [110/129] via 12.12.12.1, 00:25:16, Serial0/0
13.0.0.0/24 is subnetted, 1 subnets
O 13.13.13.0 [110/128] via 12.12.12.1, 00:25:16, Serial0/0
R3#sh ip ro os
1.0.0.0/24 is subnetted, 1 subnets
O 1.1.1.0 [110/65] via 13.13.13.1, 00:25:39, Serial0/0
2.0.0.0/24 is subnetted, 1 subnets
O 2.2.2.0 [110/129] via 13.13.13.1, 00:25:39, Serial0/0
12.0.0.0/24 is subnetted, 1 subnets
O 12.12.12.0 [110/128] via 13.13.13.1, 00:25:39, Serial0/0
注意：
此次实验，在路由器接口上采用了动态学习帧中继路由的方式，即只是指定了接口的DLCI，并没有指定frame-relay map ip。如果采用在接口上静态指定的话，即使用命令frame-relay map ip xxxx dlci xxx的话，必须指定关键字broadcast，不然无法建立ospf邻接关系。
Serial0/0 (up): ip 12.12.12.1 dlci 201(0xC9,0x3090), dynamic,
broadcast,, status defined, active
