OSPF Fundamentals

OSPF Adjacencies

OSPF creates adjacencies between neighboring routers for the purpose of exchanging routing information. Not every neighbor becomes adjacent in a ...
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/ OSPF, OSPF Intro

OSPF Area Types

Another way to reduce the route information advertised is to create a stub area. Configuring a stub area forces its ...
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/ OSPF, OSPF Area Types, OSPF Intro


Link-State Announcements When OSPF neighbors become adjacent, the LSDBs synchronize between the OSPF routers. As an OSPF router adds or ...
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/ OSPF, OSPF Intro, OSPF LSA Types

OSPF Packet Types

Type Packet Name Functionality 1 Hello Packets are sent out periodically on all OSPF interfaces to discover new neighbors while ...
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/ OSPF, OSPF Intro, OSPF Packet Types

How OSPF works?

OSPF sends to neighboring routers link-state advertisements (LSAs) that contain the link state and link metric. The received LSAs are ...
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/ OSPF, OSPF Intro


Multi-access networks such as Ethernet (LANs) and Frame Relay networks allow more than two routers to exist on a network ...
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OSPF Network Types

Different media can provide different characteristics or might limit the number of nodes allowed on a segment. Frame Relay and ...
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/ OSPF, OSPF Intro, OSPF Network Types

OSPF Advanced Topics

OSPF Route Filtering

Route filtering is a method for selectively identifying routes that are advertised or received from neighbor routers. Route filtering may ...
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/ Advanced OSPF, OSPF, OSPF Route Filtering

OSPF Path Selection

OSPF executes Dijkstra’s shortest path first (SPF) algorithm to create a loop-free topology of shortest paths. All routers use the ...
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/ Advanced OSPF, OSPF, OSPF Path Selection

OSPF Tshoot

OSPF Adjacencies Tshoot

Problem: OSPF Neighbor List is Empty This is the most common problem in OSPF neighbor relationships. The most common causes ...
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/ OSPF, OSPF Tshoot