Operation Manual – Routing ProtocolH3C S7500 Series Ethernet Switches Chapter 4 OSPF Configuration4-1Chapter 4 OSPF ConfigurationWhen configuring OSPF, go to these sections for information you are interested in:z OSPF Overviewz OSPF Configuration Task Listz Displaying and Maintaining OSPF Configurationz OSPF Configuration Examplez Troubleshooting OSPF Configuration4.1 OSPF Overview4.1.1 Introduction to OSPFOpen Shortest Path First (OSPF) is a link state interior gateway protocol developedby IETF. At present, OSPF version 2 (RFC 2328) is used, which has the followingfeatures:z High applicability: OSPF supports networks of various sizes and can support upto several hundred routers.z Fast convergence: OSPF can transmit update packets instantly after networktopology changes for routing information synchronization in the autonomoussystem (AS).z Loop-free: OSPF computes routes with the Shortest Path Tree algorithmaccording to the collected link states, so no loop routes are generated from thealgorithm itself.z Area partition: OSPF allows an autonomous system network to be divided intodifferent areas for ease of management so that routing information transmittedbetween the areas is abstracted further, thereby reducing network bandwidthconsumption.z Equivalent route: OSPF supports multiple equivalent routes to the samedestination.z Routing hierarchy: OSPF has a four-level routing hierarchy. It prioritizes theroutes as intra-area, inter-area, external type-1, and external type-2 routes.z Authentication: OSPF supports interface-based packet authentication toguarantee the security of route calculation.z Multicast transmission: OSPF supports transmitting protocol packets in multicastmode.4.1.2 OSPF Route CalculationThe following is a simple process of how OSPF calculates routes when there is noarea partition:
