Introduction:
The functioning of the Open Shortest Path First (OSPF) protocol is dependent on the underlying topology. Based on the topology, networks can be broadly classified as broadcast multi-access networks, non-broadcast multi-access networks and point-to-point networks.
OSPF network Point-to-Point is default option for point-to-point interfaces such as HDLC, PPP or point-to-point NBMA subinterface. It uses multicast hellos OSPF messages and sent it on multicast address 224.0.0.5 and there is no Designated Router (DR) and Backup DR (BDR) election.
Description:
No special design consideration needs to be taken into account for point-to-point OSPF interface. Configure OSPF on a point-to-point link by enabling an OSPF routing process and specifying the interface on which OSPF should be run.
Perform these steps:
Configure an OSPF routing process by issuing the "router ospf" command in global configuration mode.
Define the interfaces on which OSPF runs and define the area ID for those interfaces by issuing the "network area" command in router configuration mode.
Example:
R1#conf t
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)#router ospf 100
R1(config-router)#network 10.0.0.0 0.255.255.255 area 0
R1(config-router)#end
R1#
To verify the network type use "show ip ospf interface" command
R1#show ip ospf interface s0/0
Serial0/0 is up, line protocol is up
Internet Address 10.1.1.1/8, Area 0
Process ID 100, Router ID 10.1.1.1, Network Type POINT_TO_POINT, Cost: 64
Transmit Delay is 1 sec, State POINT_TO_POINT
Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
oob-resync timeout 40
Hello due in 00:00:07
Supports Link-local Signaling (LLS)
Cisco NSF helper support enabled
IETF NSF helper support enabled
Index 1/1, 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 10.1.1.2
Suppress hello for 0 neighbor(s)
For information on configuring OSPF on a point-to-point link as well as configuring OSPF on routers connected through unnumbered interfaces, refer to Initial Configurations for OSPF over a Point-to-Point Link.
