H3C Technologies H3C S10500 Series Switches - Manual (Page 93)

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Configuring a stub area
Configure a non-backbone area at the AS edge as a stub area by configuring the stub command on all
the routers attached to the area. In this way, Type-5 LSAs will not be flooded within the stub area,
reducing the routing table size. The ABR generates a default route into the stub area so all packets
destined outside of the AS are sent through the default route.
To further reduce the routing table size and routing information exchanged in the stub area, configure it
as a totally stub area by using the stub [ no-summary ] command on the ABR. In this way, neither AS
external routes nor inter-area routing information will be distributed into the area. All the packets destined
outside of the AS or area will be sent to the ABR for forwarding.
Follow these steps to configure OSPF areas:
To do… Use the command… Remarks
Enter system view system-view —
Enter OSPF view
ospf [ process-id | router-id router-id
| vpn-instance vpn-instance-name ]
* —
Enter area view area area-id —
Configure the area as a stub area stub [ no-summary ]
Required
Not configured by default.
Specify a cost for the default
route advertised to the stub area default-cost cost Optional
Defaults to 1.
NOTE:
•
You must use the stub command on routers attached to a stub area.
• Using the default-cost command only takes effect on the ABR of a stub area.
• The backbone area cannot be a totally stub area.
• A (totally) stub area cannot have an ASBR because AS external routes cannot be distributed into the stub
area.
• Virtual links cannot transit totally stub areas.
Configuring an NSSA area
A stub area cannot redistribute routes. Configure the area as an NSSA area to allow for route
redistribution by keeping other stub area characteristics.
Follow these steps to configure an NSSA area:
To do… Use the command… Remarks
Enter system view system-view —
Enter OSPF view
ospf [ process-id | router-id
router-id | vpn-instance
vpn-instance-name ] *
—
Enter area view area area-id —