OSPF Network Types

C.

The Broadcast network type is the default for an OSPF enabled ethernet interface (while Point-to-Point is the default OSPF network type for Serial interface with HDLC and PPP encapsulation)

By default, when OSPF is enabled on an interface, the type of OSPF network to which it belongs is determined by the type of Layer 2 connection used by the interface. Here is how each OSPF network type is determined:

• Point-to-Point (P2P): The interface is considered P2P when it is directly connected to a single neighbor. Examples include serial links, PPP connections, and some virtual interfaces. In this case, OSPF sends hello packets to the neighbor with a destination multicast address of 224.0.0.5, and the OSPF interface type is set to point-to-point.

• Broadcast: The interface is considered broadcast when it is connected to a multi-access network, such as Ethernet, Token Ring, or FDDI. In this case, OSPF sends hello packets to the multicast address 224.0.0.5 and expects to receive them from all other routers on the network. OSPF will use the DR/BDR election process to minimize the amount of flooding on the network.

• Non-Broadcast: The interface is considered non-broadcast when it is connected to a multi-access network that does not support multicast traffic, such as Frame Relay, X.25, or ATM. In this case, OSPF must be configured with the IP addresses of all neighboring routers so that it can send hello packets directly to them.

• Point-to-Multipoint (P2MP): The interface is considered P2MP when it is connected to multiple neighbors, but the connections are treated as P2P links. This type of interface is typically used in hub-and-spoke networks, where a single router connects to multiple remote sites. In this case, OSPF sends hello packets to the multicast address 224.0.0.5, but it sets the interface type to point-to-multipoint.

Based on the information given in the question, the Gigabit Ethernet interface is not specified as a P2P or P2MP connection, and it is not mentioned whether the network supports multicast traffic. Therefore, the default assumption is that it is a broadcast network, and the interface is considered to be part of a broadcast OSPF network. Therefore, the correct answer is C. broadcast.