OSPF messages transmitted over an Ethernet link contain the following information:
- Data Link Ethernet Frame Header - Identifies the destination multicast MAC addresses 01-00-5E-00-00-05 or 01-00-5E-00-00-06. (Figure 1)
- IP Packet Header - Identifies the IPv4 protocol field 89 which indicates that this is an OSPF packet. It also identifies one of two OSPF multicast addresses, 224.0.0.5 or 224.0.0.6. (Figure 2)
- OSPF Packet Header - Identifies the OSPF packet type, the router ID and the area ID. (Figure 3)
- OSPF Packet Type Specific Data - Contains the OSPF packet type information. The content differs depending on the packet type. In this case, it is an IPv4 Header. (Figure 4)