OSPF INTERFACE TABLE - All the router interfaces that have been configured to participate in an OSPF routing process are listed in the OSPF interface table.
OSPF NEIGHBOR TABLE - OSPF neighbors learned via Hello packets are present in an OSPF neighbor table. A neighbor is removed from this table if Hellos have not been heard from the neighbor within the dead time interval. Additionally, a neighbor is removed from this table if the interface associated with the neighbor goes down.
OSPF LINK-STATE DATABASE - The OSPF link-state database is an OSPF data structure that contains topology information for all areas in which a router participates, in addition to information about how to route traffic to networks residing in other areas or autonomous systems.
OSPF ROUTING INFORMATION BASE (RIB) - The OSPF RIB stores the results of OSPF’s shortest path first (SPF) calculations.
LINK-STATE ADVERTISEMENT (LSA) - A link-state advertisement is a message sent and received by OSPF routers to educate routers about a network topology. Various LSA types exist.
DIJKSTRA SHORTEST PATH FIRST (SPF) ALGORITHM - Dijkstra’s algorithm, which Open Shortest Path First (OSPF) uses, takes the information contained in the LSAs to determine the shortest path to any destination within an area of the network.
VIRTUAL LINK - Non-backbone Open Shortest Path First (OSPF) areas (that is, areas other than area 0) must be adjacent to the backbone area. If, however, an OSPF area is not physically adjacent to area 0, a virtual link can be constructed to interconnect the discontiguous area to area 0. A virtual link spans a transit area, which is adjacent to area 0.
OSPF INTERNAL ROUTER - All the networks directly connected to an OSPF internal router belong to the same OSPF area. Therefore, an OSPF internal router has a single link-state database.
OSPF AREA BORDER ROUTER (ABR) - An OSPF ABR connects to more than one OSPF area and therefore maintains multiple link-state databases (one for each connected area). A primary responsibility of an ABR is to exchange topological information between the backbone area and other connected areas.
OSPF BACKBONE ROUTER - An OSPF backbone router has at least one of its connected networks participating in OSPF area 0 (that is, the backbone area). If all the connected networks are participating in the backbone area, the router is also considered an internal router. Also, if a backbone router has one or more connected networks participating in another area, the backbone router is also considered an area border router (ABR).
OSPF AUTONOMOUS SYSTEM BOUNDARY ROUTER (ASBR) - An OSPF ASBR has at least one connected route participating in an OSPF area and at least one connected route participating in a different autonomous system. The primary role of an ASBR is to exchange information between an OSPF autonomous system and one or more external autonomous systems.
ROUTE REDISTRIBUTION - Route redistribution allows routes learned via one method (for example, statically configured, locally connected, or learned via a routing protocol) to be injected into a different routing protocol.
BOUNDARY ROUTER - A boundary router is a router that sits at the boundary of the routing domains to be redistributed.
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