This section includes the following topics: See the “OSPF RFC Compatibility Mode Example” section for more information. You must make adjustments to set the values identically. The default supported RFC standard for OSPFv2 may be different for Cisco NX-OS and Cisco IOS. Use the rfc1583compatibility command if your network includes routers that are only compliant with RFC1583.

It is important_ to ensure that all routers support the same RFC. RFC 2328 also introduced different selection criteria for AS-external paths. This RFC introduced a different method to calculate route summary costs which is not compatible with the calculation used by RFC1583.

Note OSPFv2 on Cisco NX-OS supports RFC 2328. For more information, see Chapter7, “Configuring OSPFv3” OSPFv2 supports IPv4, while OSPFv3 supports IPv6. Routers send most LSAs only within one area, which reduces the CPU and memory requirements for an OSPF-enabled router. You can divide OSPFv2 networks into areas. Each router then uses Dijkstra’s Shortest Path First (SPF) algorithm to build its route table. When all OSPFv2 routers have identical link-state databases, the network is converged (see the “Convergence” section). The routers then flood these received LSAs out every OSPF-enabled interface so that all OSPFv2 routers eventually have identical link-state databases. Adjacent routers shar e 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 neighbor routers try to establish adjacency, which means that the routers synchronize their link-state databases to ensure that they have identical OSPFv2 routing information. Once a neighbor is discovered, the two routers compare information in the Hello packet to determine if the routers have compatible configurations. An OSPFv2 router sends a special message, called a hello packet, out each OSPF-enabled interface to discover other OSPFv2 neighbor routers. OSPFv2 is an IETF link-state protocol (see the “Link-State Protocols” section) for IPv4 networks.

This chapter includes the following sections: This chapter describes how to configure Open Shortest Path First version 2 (OSPFv2) for IPv4 networks on the Cisco NX-OS device.

Limiting the Number of Redistributed Routes.

Configuring Filter Lists for Border Routers.

Configuring Authentication for an Interface.

Configuring Optional Parameters on an OSPFv2 Instance.

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