Digisol DG-GS4826S, Management Manual

Page: 572 / 1344

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HAPTER
21 | Unicast Routing
Configuring the Open Shortest Path First Protocol (Version 2)
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5. Click Apply
Figure 363: 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
9iborder 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 364: 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
u
"router ospf" on page 1192
u
"area default-cost" on page 1197
u
"area stub" on page 1205
C
OMMAND
U
SAGE
u
Before creating a stub, first specify the address range for the area (see
"Defining Network Areas Based on Addresses" on page 560 ). Then
create a stub as described under "Adding an NSSA or Stub" on
page 568 .
u
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