RFC 2328 / START HERE
OSPFv2, before the details
OSPF: Open Shortest Path First
OSPF helps routers inside an organization learn the network's layout and calculate paths. This RFC describes OSPF version 2 for IPv4.
The idea in one picture
Routers share link information
Each builds a network map
Paths are calculated locally
A simplified picture of the idea; the chapters explain the actual mechanisms.
Why it exists
Routers need to adapt when links or devices change without having every path manually reconfigured.
A familiar example
Routers in a campus network share link information and calculate another route after a cable fails.
Helpful background
You can start here without reading another RFC. If these ideas are unfamiliar, these short introductions may help.
What you’ll learn next
Begin with chapter one, or choose a topic.
- Discover neighbors and form adjacenciesHello exchanges discover neighbors, but not every neighbor pair needs a full adjacency.→
- Synchronize the link-state databaseDatabase Description summaries reveal missing or older LSAs before full database synchronization.→
- Flood a newer link advertisementReliable flooding distributes newer link-state information through the area.→
- Compute a shortest-path treeEach router computes routes from its link-state database using the shortest-path calculation.→
- Separate areas through the backboneOSPF divides an autonomous system into areas connected through the backbone.→
This introduction explains RFC 2328 (1998). Read the original RFC ↗