CCNA NOTES 8 # OSPF Complete Reference Guide for CCNA & CCNP | Areas, LSAs, DR/BDR & Configuration
OSPF Network Protocol Reference Notes OSPF PROTOCOL #89 · AD = 110 LAYER 3 · LINK-STATE DIJKSTRA / SPF · OPEN STD OPEN SHORTEST PATH FIRST — COMPLETE REFERENCE 01 Protocol Overview Metric 100 / BW Cost = 100 ÷ Interface BW (Mbps) Algorithm SPF Dijkstra Shortest Path First Key concept — Routes are never directly advertised. Complete topology data (LSAs) floods the domain. Each router independently runs SPF to calculate its best paths. Interface Speed Default Cost Ethernet 10 Mbps 10 FastEthernet 100 Mbps 1 Serial (T1) 1.544 Mbps 64 02 Areas & Router Types Rule — Area 0 is the backbone and must be central. All non-backbone areas must connect to Area 0, directly or via a Virtual Link. Only one Area 0 per domain. Router Type Definition Generates Backbone Router All interfaces in Area 0 LSA 1 Non-Backbone Router All interfaces in a non-backbone area LSA 1 ABR Interface in Area 0 + at least one other area. Holds full LSDB of each connecte...