R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide

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Configuration prerequisites
Before you configure an OSPF area, complete the following tasks:
• Configure IP addresses for interfaces.
• 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 are not distributed into the area. All the packets destined outside of the area
are sent to the ABR for forwarding.
To configure an OSPF stub area:
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.
You cannot configure the
backbone area as a stub or totally
stub area.
A stub or totally stub area cannot
have an ASBR because external
routes cannot be distributed into
the area.
5. Specify a cost for the default
route advertised to the stub
area.
default-cost cost
Optional.
The default cost is 1.
The default-cost command takes
effect only on the ABR of a stub
area or totally stub area.
NOTE:
V
irtual links cannot transit a stub area or totally stub area.
Configuring an NSSA area
A stub area cannot import external routes, but an NSSA area can import external routes into the OSPF
routing domain while keeping other stub area characteristics.