Default Routes - Lenovo RackSwitch G8264 Application Manual

Default Routes

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When an OSPF routing device encounters traffic for a destination address it does
not recognize, it forwards that traffic along the default route. Typically, the default
route leads upstream toward the backbone until it reaches the intended area or an
external router.
Each G8264 acting as an ABR automatically inserts a default route into stub and
NSSA attached areas. In simple OSPF stub areas or NSSAs with only one ABR
leading upstream (see Area 1 in Figure
outside the area is forwarded to the switch's IP interface, and then into the
connected transit area (usually the backbone). Since this is automatic, no further
configuration is required for such areas.
Figure 50. Injecting Default Routes
If the switch is in a transit area and has a configured default gateway, it can inject a
default route into rest of the OSPF domain. Use the following command to
configure the switch to inject OSPF default routes (Router OSPF mode):
RS G8264(config­router­ospf)# default­information <metric value> <metric type (1 or
2)>
In this command, <metric value> sets the priority for choosing this switch for
default route. The value none sets no default and 1 sets the highest priority for
default route. Metric type determines the method for influencing routing decisions
for external routes.
When the switch is configured to inject a default route, an AS‐external LSA with
link state ID 0.0.0.0 is propagated throughout the OSPF routing domain. This LSA
is sent with the configured metric value and metric type.
The OSPF default route configuration can be removed with the command:
RS G8264(config­router­ospf)# no default­information
50), any traffic for IP address destinations
Chapter 35: Open Shortest Path First
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