Cisco NCS 5500 Series

• The router ID is a 32-bit number with no relationship to an IPv6 address.
OSPF Hierarchical CLI and CLI Inheritance
Hierarchical CLI is the grouping of related network component information at defined hierarchical levels such
as at the router, area, and interface levels. Hierarchical CLI allows for easier configuration, maintenance, and
troubleshooting of OSPF configurations. When configuration commands are displayed together in their
hierarchical context, visual inspections are simplified. Hierarchical CLI is intrinsic for CLI inheritance to be
supported.
With CLI inheritance support, you need not explicitly configure a parameter for an area or interface. In the
software, the parameters of interfaces in the same area can be exclusively configured with a single command,
or parameter values can be inherited from a higher hierarchical level—such as from the area configuration
level or the router ospf configuration levels.
For example, the hello interval value for an interface is determined by this precedence “IF” statement:
If the hello interval command is configured at the interface configuration level, then use the interface configured
value, else
If the hello interval command is configured at the area configuration level, then use the area configured value,
else
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.
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 4: OSPF Routing Components
This figure illustrates the routing components in an OSPF network topology.
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x
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Implementing OSPF
OSPF Hierarchical CLI and CLI Inheritance