Ospf Routing Components; Autonomous Systems; Areas - Cisco ASR 9000 Series Configuration Manual

OSPF Routing Components

OSPF Routing Components
Before implementing OSPF, you must know what the routing components are and what purpose they serve.
They consist of the autonomous system, area types, interior routers, ABRs, and ASBRs.
This figure illustrates the routing components in an OSPF network topology.
Figure 16: OSPF Routing Components

Autonomous Systems

The autonomous system is a collection of networks, under the same administrative control, that share routing
information with each other. An autonomous system is also referred to as a routing domain.
Routing Components, on page 336
can consist of one or more OSPF areas.

Areas

Areas allow the subdivision of an autonomous system into smaller, more manageable networks or sets of
adjacent networks. As shown in
109 consists of three areas: Area 0, Area 1, and Area 2.
OSPF hides the topology of an area from the rest of the autonomous system. The network topology for an
area is visible only to routers inside that area. When OSPF routing is within an area, it is called intra-area
routing. This routing limits the amount of link-state information flood into the network, reducing routing
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
336
shows two autonomous systems: 109 and 65200. An autonomous system
Figure 16: OSPF Routing Components, on page
Implementing OSPF
Figure 16: OSPF
336, autonomous system
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