Open Shortest Path First (OSPFv2) | 355
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Open Shortest Path First (OSPFv2)
This chapter includes the following topics:
• Overview
• Implementing OSPF with FTOS
• Fast Convergence (OSPFv2, IPv4 only)
• Multi-Process OSPF (OSPFv2, IPv4 only)
• RFC-2328 Compliant OSPF Flooding
• OSPF ACK Packing
• OSPF Adjacency with Cisco Routers
• Configuration Information
• Configuration Task List for OSPFv2 (OSPF for IPv4)
• Troubleshooting OSPFv2
• Sample Configurations for OSPFv2
OSPF protocol standards are listed in the Chapter 40, Standards Compliance chapter.
Overview
Open shortest path first (OSPF) routing is a link-state routing protocol that calls for the sending of
link-state advertisements (LSAs) to all other routers within the same autonomous system (AS) areas.
Information on attached interfaces, metrics used, and other variables is included in OSPF LSAs. As OSPF
routers accumulate link-state information, they use the shortest path first algorithm (SPF algorithm) to
calculate the shortest path to each node.
OSPF routers initially exchange HELLO messages to set up adjacencies with neighbor routers. Use the
HELLO process to establish adjacencies between routers of the AS. It is not required that every router
within the autonomous system areas establish adjacencies. If two routers on the same subnet agree to
become neighbors through the HELLO process, they begin to exchange network topology information in
the form of LSAs.
In OSPFv2, neighbors on broadcast and NBMA links are identified by their interface addresses, while
neighbors on other types of links are identified by RID.
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