R3721-F3210-F3171-HP High-End Firewalls Network Management Configuration Guide-6PW101

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Configuring OSPF areas
After splitting an OSPF AS into multiple areas, you can further configure some areas as stub areas or
NSSA areas as needed.
If no connection can be achieved between the backbone and a non-backbone area, or within the
backbone itself, you can configure virtual links to solve it.
Configuration prerequisites
Before configuring an OSPF area, you have configured:
• Configure IP addresses for interfaces, making neighboring nodes accessible with each other at the
network layer.
• Configure OSPF basic functions.
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 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, 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.
To configure OSPF areas:
Ste
p
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.
5. Specify a cost for the default
route advertised to the stub
area.
default-cost cost
Optional.
Defaults to 1.
NOTE:
• You are required to 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. You can configure the area as an NSSA area to allow for route
redistribution by keeping other stub area characteristics.