ProLiant BL p-Class GbE2 Interconnect Switch Application Guide

OSPF 111
OSPF
GbE2 software supports the Open Shortest Path First (OSPF) routing protocol. The GbE2 implementation
conforms to the OSPF version 2 specifications detailed in Internet RFC 1583. The following sections discuss OSPF
support for the GbE2 Interconnect Switch:
• OSPF Overview—This section provides information on OSPF concepts, such as types of OSPF areas, types
of routing devices, neighbors, adjacencies, link state database, authentication, and internal versus external
routing.
• OSPF Implementation in GbE2 Software—This section describes how OSPF is implemented in GbE2
software, such as configuration parameters, electing the designated router, summarizing routes, defining
route maps and so forth.
• OSPF Configuration Examples—This section provides step-by-step instructions on configuring different
configuration examples:
• Creating a simple OSPF domain
• Creating virtual links
• Summarizing routes
OSPF overview
OSPF is designed for routing traffic within a single IP domain called an Autonomous System (AS). The AS can be
divided into smaller logical units known as areas.
All routing devices maintain link information in their own Link State Database (LSDB). The LSDB for all routing
devices within an area is identical but is not exchanged between different areas. Only routing updates are
exchanged between areas, thereby significantly reducing the overhead for maintaining routing information on a
large, dynamic network.
The following sections describe key OSPF concepts.
Types of OSPF areas
An AS can be broken into logical units known as areas. In any AS with multiple areas, one area must be
designated as area 0, known as the backbone. The backbone acts as the central OSPF area. All other areas in
the AS must be connected to the backbone. Areas inject summary routing information into the backbone, which
then distributes it to other areas as needed.
OSPF defines the following types of areas:
• Stub Area—an area that is connected to only one other area. External route information is not distributed
into stub areas.
• Not-So-Stubby-Area (NSSA)—similar to a stub area with additional capabilities. Routes originating from
within the NSSA can be propagated to adjacent transit and backbone areas. External routes from outside
the AS can be advertised within the NSSA but are not distributed into other areas.
• Transit Area—an area that allows area summary information to be exchanged between routing devices.
The backbone (area 0), any area that contains a virtual link to connect two areas, and any area that is not
a stub area or an NSSA are considered transit areas