If the hello interval command is configured at the router ospf configuration level, then use the router ospf
configured value, else
Use the default value of the command.
Understanding hierarchical CLI and CLI inheritance saves you considerable configuration time. See Configuring
Authentication at Different Hierarchical Levels for OSPF Version 2, on page 288 to understand how to
implement these fundamentals. In addition, Cisco IOS XR Software examples are provided in Configuration
Examples for Implementing OSPF , on page 334.
Tip
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 15: OSPF Routing Components
This figure illustrates the routing components in an OSPF network topology.
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 15: OSPF
Routing Components, on page 261 shows two autonomous systems: 109 and 65200. An autonomous system
can consist of one or more OSPF areas.
Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
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Implementing OSPF
OSPF Routing Components