LevelOne GTL-2691 - Manual (Page 682)

C HAPTER 20 | Unicast Routing
Configuring the Open Shortest Path First Protocol (Version 2)
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5. Click Apply
Figure 432: Configuring Protocol Settings for an NSSA
C ONFIGURING S TUB
S ETTINGS
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 433: 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 R EFERENCES
◆ "router ospf" on page 1476
◆ "area default-cost" on page 1481
◆ "area stub" on page 1489
C OMMAND U SAGE
◆ Before creating a stub, first specify the address range for the area (see
"Defining Network Areas Based on Addresses" on page 670 ). Then
create a stub as described under "Adding an NSSA or Stub" on
page 678 .
◆ 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