Handbook

N8406-023 1Gb Intelligent L3 Switch Application Guide 115
To resolve the situation and select one default route among multiple choices in an area, you can manually
configure a metric value on each ABR. The metric assigns a priority to the ABR for its selection as the priority
default route in an area. The following command is used for setting the metric value:
>> # /cfg/l3/ospf/default <metric value> <metric type (1 or 2)>
where <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.
To clear a default route metric from the switch, use the following command:
>> # /cfg/l3/ospf/default none
Virtual links
Usually, all areas in an OSPF AS are physically connected to the backbone. In some cases where this is not
possible, you can use a virtual link. Virtual links are created to connect one area to the backbone through another
non-backbone area.
The area which contains a virtual link must be a transit area and have full routing information. Virtual links cannot
be configured inside a stub area or NSSA. The area type must be defined as transit using the following
command:
>> # /cfg/l3/ospf/aindex <area index>/type transit
The virtual link must be configured on the routing devices at each endpoint of the virtual link, though they may
traverse multiple routing devices. To configure a switch as one endpoint of a virtual link, use the following command:
>> # /cfg/l3/ospf/virt <link number>/aindex <area index>/nbr <router ID>
where <link number> is a value between 1 and 3, <area index> is the OSPF area index of the transit area, and
<router ID> is the IP address of the virtual neighbor (nbr), the routing device at the target endpoint. Another router
ID is needed when configuring a virtual link in the other direction. To provide the switch with a router ID, see
―Router ID.‖
For a detailed configuration example on Virtual Links, see ―Example 2: Virtual Links.‖