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CCNA: OSPF tutorial

Let jump into the world of OSPF

OSPF or Open Shortest Path First is a widely used protocol in this planet. Why ? just because it’s a open standard and non-proprietary. This is the reason Cisco made a rival of this protocol called EIGRP(enhanced interior gateway routing protocol).

Some of the basic information before we begin..

  • OSPF is a link state routing protocol .
  • Is a open standard non-proprietary routing protocol means any device or vendor can use this protocol for routing.
  • Based on  Dijkstra algorithm
  • Routing information is shared through Link-state updates (LSAs) via multicasting.
  • OSPF is a classless routing protocol and sends subnet mask on each routing updates.
  • Support VLSM and route summrization.
  • Metric calculation is based on inverse of bandwidth.

Only generate routing table occurred in network topology. When changes detected by the OSPF it create a LSA (link state advertisement) and send to all neighbor devices. Every neighbor devices update it’s LSDB (link state database) and forward LSA to his neighbor devices.