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Open Shortest Path First

What Does Open Shortest Path First Mean?

Open Shortest Path First (OSPF) is a link state routing protocol (LSRP) that uses the Shortest Path First (SPF) network communication algorithm (Dijkstra’s algorithm) to calculate the shortest connection path between known devices.


Techopedia Explains Open Shortest Path First

OSPF bis an Interior Gateway Protocol (IGP) that routes Internet Protocol (IP) packets within a single routing network domain only. OSPF finds the best network layout (topology) by calculating shortest device connection paths using the Shortest Path First (SPF) algorithm.

For example, a person in city A wants to travel to city M and is given two options:

  • Travel via cities B and C. The route would be ABCM. And the distance (or bandwidth cost in the networking case) for A-B is 10 miles, B-C is 5 miles and C-M is 10 miles.
  • Travel via city F. The route would be AFM. And the distance for A-F is 20 miles and F-M is 10 miles.

The shortest route is always the one with least amount of distance covered in total. Thus, the ABCM route is the better option (10+5+10=25), even though the person has to travel to two cities as the associated total cost to travel to the destination is less than the second option with a single city (20+10=30). OSPF performs a similar algorithm by first calculating the shortest path between the source and destination based on link bandwidth cost and then allows the network to send and receive IP packets via the shortest route.


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