HP 200 Series Services And Applications page 264

Routing with OSPF
OSPF (Open Shortest Path First) is a new IP routing protocol. HP routers
implement Version 2 of OSPF, which is documented in RFC 1247. Unlike RIP,
OSPF employs a link-state algorithm (also referred to as a shortest-path-first
(SPF) algorithm). Link-state algorithms are those in which each routing
node floods information about its attached links to all other routing nodes.
Area C
Area ID 3.0.0.0
Backbone
Virtual Link
Area A
Area B
Area ID 1.0.0.0
Area ID 2.0.0.0
Stub Area
Area
Borders
OSPF Backbone
Area ID 0.0.0.0
RIP or EGP
External
Area D
Network
Area ID 4.0.0.0
Figure 1. OSPF Autonomous System
Figure 1 shows an OSPF AS (autonomous system). AS is an IP term that
refers to a collection of routers that all use the same IGP (interior gateway
protocol). IGP is also an IP term. It refers to a routing protocol run within an
AS. IGPs are a subset of routing protocols. They are referred to as IGPs to
distinguish them from EGPs (exterior gateway protocols), another type of
routing protocol. EGPs are used to route data between ASs. The Exterior
Gateway Protocol (also known as EGP) is also the name of a specific EGP.
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