Comparison Of Cisco Ios Xr Software Ospfv3 And Ospfv2; Ospf Hierarchical Cli And Cli Inheritance - Cisco ASR 9000 Series Routing Configuration Manual

Implementing OSPF
• OSPF over demand circuit—RFC 1793 is supported.

Comparison of Cisco IOS XR Software OSPFv3 and OSPFv2

Much of the OSPFv3 protocol is the same as in OSPFv2. OSPFv3 is described in RFC 2740.
The key differences between the Cisco IOS XR Software OSPFv3 and OSPFv2 protocols are as follows:
• OSPFv3 expands on OSPFv2 to provide support for IPv6 routing prefixes and the larger size of IPv6
• When using an NBMA interface in OSPFv3, users must manually configure the router with the list of
• Unlike in OSPFv2, multiple OSPFv3 processes can be run on a link.
• LSAs in OSPFv3 are expressed as "prefix and prefix length" instead of "address and mask."
• The router ID is a 32-bit number with no relationship to an IPv6 address.

OSPF Hierarchical CLI and CLI Inheritance

Cisco IOS XR Software introduces new OSPF configuration fundamentals consisting of 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
Cisco IOS XR 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.
addresses.
neighbors. Neighboring routers are identified by the link local address of the attached interface of the
neighbor.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
Comparison of Cisco IOS XR Software OSPFv3 and OSPFv2
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