H3C Technologies H3C S3600 Series Switches - Manual (Page 340)

4-13
To do... Use the command... Remarks
Enter system view system-view —
Configure the router ID router id router-id
Optional
If multiple OSPF processes run on a
router, you are recommended to use
the router-id keyword in the ospf
command to specify different router
IDs for different processes.
Enable OSPF and enter
OSPF view ospf [ process-id
[ router-id router-id ] ]
Required
Enter OSPF view.
Enter OSPF area view area area-id —
Configure the network
segments in the area network ip-address
wildcard-mask
Required
By default, an interface does not
belong to any area.
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 An OSPF process ID on a router must be unique.
z One segment can belong to only one area and you must specify each OSPF interface to belong to
a particular area.
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.
Type-7 LSAs can be advertised in an NSSA. Type-7 LSAs are generated by ASBRs in the NSSA, and
will be transformed into Type-5 LSAs (AS-external LSAs) when 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.