H3C Technologies H3C S7500E Series Switches - Manual (Page 94)

4-25
Configuring a Stub Area
You can 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, which describe AS external
routes, will not be flooded within the stub area, reducing the routing table size. The ABR generates a
default route into the stub area so that 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, you can
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
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.
z It is required to use the stub command on routers attached to a stub area.
z Using the default-cost command only takes effect on the ABR of a stub area.
z The backbone area cannot be a (totally) stub area.
z A (totally) stub area cannot have an ASBR because AS external routes cannot be distributed into
the stub area.
z Virtual links cannot transit (totally) stub areas.
Configuring an NSSA Area
A stub area cannot redistribute routes. You can configure the area as an NSSA area to allow for route
redistribution while keeping other characteristics of a stub area.
Follow these steps to configure an NSSA area: