BSCI - OSPF - Network Types - Point-to-Point

Point-to-Point:

Uses Sub-Interfaces
Sub-interfaces used to address Split-Horizon issues that can result in using a single physical interface
Separate sub-interfaces require separate subnets
No DR/BDR elections
Neighbors automatically form.

Configuration:
Lacking a diagram, assume we have 4 routers in a hub and spoke design. R1 is the Hub and R2,R3, and R4 are spoke routers. Frame-relay is in use.

On R1:
R1(Config)#router ospf 1
R1(config-router)#network 192.168.0.0 0.0.255.255 area 0
!
R1(config)#int s0/0
R1(config-if)#encapsulation frame-relay
R1(config-if)#no shutdown
!
R1(config)#int s0/0.102 point-to-point
R1(config-if)#description Link_To_R2
R1(config-if)#ip addr 192.168.12.1 255.255.255.252
R1(config-if)#frame-relay interface-dlci 102
!
R1(config)#int s0/0.103 point-to-point
R1(config-if)#description Link_To_R3
R1(config-if)#ip addr 192.168.13.1 255.255.255.252
R1(config-if)#frame-relay interface-dlci 103
!
R1(config)#int s0/0.104 point-to-point
R1(config-if)#description Link_To_R4
R1(config-if)#ip addr 192.168.14.1 255.255.255.252
R1(config-if)#frame-relay interface-dlci 104
!

On R2:
R2(Config)#router ospf 1
R2(config-router)#network 192.168.0.0 0.0.255.255 area 0
!
R2(config)#int s0/0
R2(config-if)#encapsulation frame-relay
R2(config-if)#no shutdown
!
R2(config)#int s0/0.25
R2(config-if)#description Link_To_R1
R2(config-if)#ip addr 192.168.12.2 255.255.255.252
R2(config-if)#frame-relay interface-dlci 25
!

On R3:
R3(Config)#router ospf 1
R3(config-router)#network 192.168.0.0 0.0.255.255 area 0
!
R3(config)#int s0/0
R3(config-if)#encapsulation frame-relay
R3(config-if)#no shutdown
!
R3(config)#int s0/0.35
R3(config-if)#description Link_To_R1
R3(config-if)#ip addr 192.168.13.2 255.255.255.252
R3(config-if)#frame-relay interface-dlci 35
!

On R4:
R4(Config)#router ospf 1
R4(config-router)#network 192.168.0.0 0.0.255.255 area 0
!
R4(config)#int s0/0
R4(config-if)#encapsulation frame-relay
R4(config-if)#no shutdown
!
R4(config)#int s0/0.45
R4(config-if)#description Link_To_R1
R4(config-if)#ip addr 192.168.14.2 255.255.255.252
R4(config-if)#frame-relay interface-dlci 45
!