HP 445946-001 - Manual (Page 131)

OSPF
131
OSPF
The HP 10GbE switch software supports the Open Shortest Path First (OSPF) routing protocol. The switch
implementation conforms to the OSPF version 2 specifications detailed in Internet RFC 1583. The
following sections discuss OSPF support for the HP 10GbE 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 HP 10GbE switch software. This section describes how OSPF is
implemented in switch 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. External routes from
outside the AS can be advertised within the NSSA but only if they are originated by a router from
inside the NSSA area. External routes originated by a router that is not a member of the NSSA area
are not advertised in the NSSA area.
• 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