H3C Technologies H3C S12500 Series Switches - Manual (Page 93)

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Configuration prerequisites
Before you configure an OSPF area, complete the following tasks:
• Configure IP addresses for interfaces to ensure IP connectivity between neighboring nodes.
• Enable OSPF.
Configuring a stub area
You can configure a non-backbone area at an AS edge as a stub area. To do so, issue the stub command
on all the routers attached to the area. The routing table size is reduced because Type-5 LSAs are not
flooded within the stub area. 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, you can
configure it as a totally stub area by using the stub no-summary command on the ABR. AS external
routes and inter-area routes will not be distributed into the area. All the packets destined outside of the
AS or area will be sent to the ABR for forwarding.
To configure OSPF areas:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter OSPF view.
ospf [ process-id | router-id router-id
| vpn-instance vpn-instance-name ]
*
N/A
3. Enter area view. area area-id N/A
4. Configure the area as a stub
area.
stub
[ default-route-advertise-always |
no-summary ] *
Not configured by default.
You cannot configure the
backbone area as a stub or totally
stub area.
5. Specify a cost for the default
route advertised to the stub
area.
default-cost cost
Optional.
Defaults to 1.
The default-cost command only
takes effect on the ABR of a stub
area.
NOTE:
Virtual links cannot transit (totally) stub areas.
Configuring an NSSA area
A stub area cannot redistribute routes, but an NSSA area can import external routes into the OSPF
routing domain while keeping other characteristics of a stub area. To configure an NSSA area, issue the
nssa command on all the routers attached to the area.
To configure an NSSA area: