ECS4660-28F_Management Guide-R03

C HAPTER 20 | Unicast Routing
Configuring the Open Shortest Path First Protocol (Version 2)
– 802 –
5. Click Apply
Figure 495: Configuring Protocol Settings for an NSSA
CONFIGURING
STUB SETTINGS
Use the Routing Protocol > OSPF > Area (Configure Area – Configure Stub
Area) page to configure protocol settings for a stub.
A stub does not accept external routing information. Instead, an area
border router adjacent to a stub can be configured to send a default
external route into the stub for all destinations outside the local area or the
autonomous system. This route will also be advertised as a single entry
point for traffic entering the stub. Using a stub can significantly reduce the
amount of topology data that has to be exchanged over the network.
Figure 496: OSPF Stub Area
By default, a stub can only pass traffic to other areas in the autonomous
system through the default external route. However, an area border router
can also be configured to send Type 3 summary link advertisements into
the stub about subnetworks located elsewhere in the autonomous system.
CLI REFERENCES
◆ "router ospf" on page 1751
◆ "area default-cost" on page 1756
◆ "area stub" on page 1764
COMMAND USAGE
◆ Before creating a stub, first specify the address range for the area (see
"Defining Network Areas Based on Addresses" on page 790). Then
create a stub as described under "Adding an NSSA or Stub" on
page 798.
◆ Stubs cannot be used as a transit area, and should therefore be placed
at the edge of the routing domain.
backbone
stub
ABR
default
external
route