Open Shortest Path First (OSPF) runs over the Internet Protocol’s network layer. So, Open Shortest Path First (OSPF) encapsulated only by IP and local data-link headers. Encapsulating OSPF messages transmitting over an Ethernet link contain the following information:
- Data Link Frame Header– This header contains the destination multicast MAC addresses.
- IP Packet Header–This header contains the IPv4 protocol field 89 indicates an OSPF packet. It also identifies one of two OSPF multicast addresses, 220.127.116.11 or 18.104.22.168.
- OSPF Packet Header–This header shows the OSPF packet type and also show the router ID and the area ID.
- OSPF Packet Type Specific Data– This header contains the OSPF packet type information