Implementing OSPF on Cisco IOS XR Software
Information About Implementing OSPF on Cisco IOS XR Software
RC-174
Cisco IOS XR Routing Configuration Guide
Tip Understanding hierarchical CLI and CLI inheritance saves you considerable configuration time. See the
“Configuring Authentication at Different Hierarchical Levels for OSPF Version 2” section on page 194
to understand how to implement these fundamentals. In addition, Cisco IOS XR examples are provided
in the “Configuration Examples for Implementing OSPF on Cisco IOS XR Software” section on
page 236.
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.
Figure 10 illustrates the routing components in an OSPF network topology.
Figure 10 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.
Figure 10 shows two autonomous systems: A and B. An autonomous system can consist of one or more
OSPF areas.
88721
Area 2
stub area
Area 0
backbone
R2
R3
R1
Area 1
Area 3
ABR 2
OSPF Domain
(BGP autonomous
system 109)
OSPF Domain
(BGP autonomous
system 65200)
ABR 1
ASBR 1
ASBR 2