Operation Manual – Routing Protocol
H3C S3600 Series Ethernet Switches-Release 1510 Chapter 4
OSPF Configuration
4-12
Note:
z 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.
z Router IDs can be re-selected. A re-selected router ID takes effect only after the
OSPF process is restarted.
z The ospf [ process-id [ router-id router-id ] ] command is recommended for
configuring router IDs manually.
z The ID of an OSPF process or OSPF multi-instance is unique. That is, the ID of
OSPF multi-instance must be different from any in-use process ID.
z 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 import any external route. For this reason the concept of NSSA
area is introduced. Type7 LSAs can be advertised in an NSSA area. Type7 LSAs are
generated by ASBRs of the NSSA area, and will be transformed into 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:
z Configuring the network layer addresses of interfaces so that the adjacent nodes
are reachable to each other at the network layer
z Performing basic OSPF configuration
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