Ospf Area Attribute Configuration; Configuring Ospf Area Attributes - H3C S5600 Series Operation Manual

Operation Manual – Routing Protocol
H3C S5600 Series Ethernet Switches
Note:
In router ID selection, the priorities of the router IDs configured with the ospf
[ process-id [ router-id router-id ] ] command, the router id command, and the
priorities of the router IDs automatically selected are in a descending order.
Router IDs can be re-selected. A re-selected router ID takes effect only after the
OSPF process is restarted.
The ospf [ process-id [ router-id router-id ] ] command is recommended for
configuring router IDs manually.
An OSPF process ID on a router must be unique.
One segment can belong to only one area and you must specify each OSPF
interface to belong to a particular area.

4.4 OSPF Area Attribute Configuration

Area partition in OSPF reduces the number of LSAs in the network and enhances
OSPF scalability. To further reduce routing table size and the number of LSAs in some
non-backbone areas on the edge of the AS, you can configure these areas as stub
areas.
A stub area cannot redistribute any external route. For this reason the concept of
NSSA is introduced. Type7 LSAs can be advertised in an NSSA. Type7 LSAs are
generated by ASBRs in the NSSA, and will be transformed into Type-5 LSAs
(AS-external LSAs) whey reaching ABRs in the NSSA area, which will then be
advertised to other areas.
After area partition, the OSPF route updates between non-backbone areas are
exchanged by way of the backbone area. Therefore, OSPF requires that all the
non-backbone areas should keep connectivity with the backbone area and the
backbone area must keep connectivity in itself.
If the physical connectivity cannot be ensured due to various restrictions, you can
configure OSPF virtual links to satisfy this requirement.
4.4.1 Configuration Prerequisites
Before configuring OSPF area attributes, perform the following tasks:
Configuring the network layer addresses of interfaces so that the adjacent nodes
are reachable to each other at the network layer
Performing basic OSPF configuration

4.4.2 Configuring OSPF Area Attributes

Follow these steps to configure OSPF area attributes:
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Chapter 4 OSPF Configuration