OSPF Network Types on Encapsulation PPP Interface

B.

The default OSPF network type on a PPP encapsulated serial interface is point-to-point. When a user types "show ip ospf interface" command on R1 or R2, the output will show the network type as "point-to-point" for the PPP interface connecting R1 and R2.

The OSPF network type determines the way OSPF packets are sent and received on an interface. OSPF supports the following network types:

1. Broadcast: This network type is used when an interface is connected to a broadcast network such as Ethernet. In this type, the OSPF router sends multicast OSPF packets to the "all OSPF routers" multicast address (224.0.0.5) and expects to receive multicast packets from other OSPF routers on the network.

2. Non-broadcast: This network type is used when an interface is connected to a non-broadcast network such as Frame Relay. In this type, OSPF routers send unicast OSPF packets to each other instead of multicast packets.

3. Point-to-point: This network type is used when an interface is connected to a point-to-point link such as a serial link. In this type, OSPF routers send unicast OSPF packets to each other, similar to the non-broadcast network type.

4. Point-to-multipoint: This network type is used when an interface is connected to a point-to-multipoint link such as a hub-and-spoke Frame Relay network. In this type, OSPF routers send multicast OSPF packets to the "all OSPF routers" multicast address, but also exchange unicast packets with each other.

In this scenario, the serial interface between R1 and R2 is running PPP encapsulation, which is a point-to-point protocol. Therefore, the default OSPF network type on this interface is point-to-point. This means that OSPF packets will be sent and received using unicast transmission.