OSPF Network point-to-point

Today we will talk about a single command related to the Open Shortest Path First “OSPF” which is “ip OSPF network point-to-point”. This command manually sets the OSPF network type to point-to-point. This is the default for serial links. The point-to-point network type does not have a DR election.
Note: Point-to-point can only have a single adjacency over a link.

Command is per interface:

Router(config-if)#ip ospf network point-to-point

– We have two routers “R1 & R2”  connected in a network through their S1/1 interfaces.

First, we’ll configure OSPF on R1 and R3 for their S1/1 interfaces

R1(config-router)#router ospf 1
R1(config-router)#network area 0

Next, we’ll configure the serial link to use point-to-point network type.

R1(config)#int s0/0
R1(config-if)#ip ospf network point-to-point

Then we check the network type by typing: show ip ospf interface s1/1.

Serial1/1 is up, line protocol is up
Internet Address, Area 0
Process ID 1, Router ID, 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 00:00:02
Supports Link-local Signaling (LLS)
Index 3/3, 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 1, Adjacent neighbor count is 1
Adjacent with neighbor
Suppress hello for 0 neighbor(s)

After we configure the network-area statement, the adjacency comes up.
Notice there is no DR information in the show ip ospf neighbor output. This is because the network type doesn’t support election

R1#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface 0 FULL/ – 00:00:30 Serial1/1

For any further inquires do not hesitate to contact me at osama@blog.experit.org, waiting for your comments and feedbacks.