Cisco Nexus 7000 Series - CHAPTER 6 Configuring Ospfv2; Information about Ospfv2

CHAPTER
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6-1
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
6
Configuring OSPFv2
This chapter describes how to configure Open Shortest Path First version 2 (OSPFv2) for IPv4 networks.
This chapter includes the following sections:
• Information About OSPFv2, page 6-1
• Licensing Requirements for OSPFv2, page 6-12
• Prerequisites for OSPFv2, page 6-13
• Configuration Guidelines and Limitations, page 6-13
• Configuring Basic OSPFv2, page 6-13
• Configuring Advanced OSPFv2, page 6-23
• Verifying the OSPFv2 Configuration, page 6-44
• Displaying OSPFv2 Statistics, page 6-45
• OSPFv2 Example Configuration, page 6-45
• Default Settings, page 6-45
• Additional References, page 6-46
• Feature History for OSPFv2, page 6-47
Information About OSPFv2
OSPFv2 is an IETF link-state protocol (see the “Link-State Protocols” section on page 1-9) for IPv4
networks. An OSPFv2 router sends a special message, called a hello packet, out each OSPF-enabled
interface to discover other OSPFv2 neighbor routers. Once a neighbor is discovered, the two routers
compare information in the Hello packet to determine if the routers have compatible configurations. The
neighbor routers attempt to establish adjacency, which means that the routers synchronize their
link-state databases to ensure that they have identical OSPFv2 routing information. Adjacent routers
share link-state advertisements (LSAs) that include information about the operational state of each link,
the cost of the link, and any other neighbor information. The routers then flood these received LSAs out
every OSPF-enabled interface so that all OSPFv2 routers eventually have identical link-state databases.
When all OSPFv2 routers have identical link-state databases, the network is converged (see the
“Convergence” section on page 1-6). Each router then uses Dijkstra’s Shortest Path First (SPF)
algorithm to build its route table.
You can divide OSPFv2 networks into areas. Routers send most LSAs only within one area, which
reduces the CPU and memory requirements for an OSPF-enabled router.