OSPF Protocol Configuration Overview

The OSPF routing protocol operates within a single autonomous system (AS). A router running OSPF distributes its state information (such as usable interfaces and neighbor reachability) by periodically flooding link-state advertisements (LSAs) throughout the AS.

Each OSPF router uses LSAs from neighboring routers to maintain a linkstate database, a listing of topology and state information for the surrounding networks. The constant distribution of LSAs throughout the routing domain enables all routers in an AS to maintain identical link-state databases. OSPF uses the link-state database to determine the best path to any network within the AS by generating a shortest-path tree (a graphical representation of the shortest path to any network within the AS). While all routers have the same link-state database, they all have unique shortest-path trees because a router always generates the tree with itself at the top of the tree.

To enable OSPF on a security device, you must first enable OSPF on a virtual router, and then enable OSPF on individual interfaces. You can also configure optional OSPF settings, such as the following:

Additionally, you can set security-related OSPF settings at either the VR level or on a per-interface basis. The following topics detail how to enable OSPF and configure all optional parameters.

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