OSPF(Open Shortest Path First)
1. What is OSPF? OSPF (Open Shortest Path First) is Link State IGP Dynamic Routing protocol that operates directly over IP using protocol number 89 and AD 110. OSPF exchanges link state information using LSA (link state advertisement) to build LSDB (link state database) which represents complete network topology. OSPF runs SPF (shortest path first) also known as Dijkstra’s Algorithm on LSDB to calculate shortest path tree and selects best path based on metric called cost, which is derived from interface Bandwidth. Cost=reference BW(default:100Mbps)/interface BW) but can change reference bandwidth with “auto-cost reference-bandwidth xxxxxx” OSPF uses hierarchical multi-area design with area 0 as backbone to reduce LSDB size, limit SPF recalculations, and improve scalability and convergence in large networks. 2. What are OSPF Features? 1.Fast Convergence -hello and dead timers for neighbor failure detection -Supports fast hello by using hello-multiplier comman...
