OSPF
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8. Define the transit area.
>> OSPF Area (index) 0 # ../aindex 1 (Select menu for area index 1)
>> OSPF Area (index) 1 # areaid 0.0.0.1(Set the area ID for OSPF area 1)
>> OSPF Area (index) 1 # type transit (Define area as transit type)
>> OSPF Area (index) 1 # enable (Enable the area)
9. Define the stub area.
>> OSPF Area (index) 1 # ../aindex 2 (Select the menu for area index 2)
>> OSPF Area (index) 2 # areaid 0.0.0.2(Set the area ID for OSPF area 2)
>> OSPF Area (index) 2 # type stub (Define area as stub type)
>> OSPF Area (index) 2 # enable (Enable the area)
10. Attach the network interface to the backbone.
>> OSPF Area (index) 2 # ../if 1 (Select OSPF menu for IP interface 1)
>> OSPF Interface 1 # aindex 1 (Attach network to transit area index)
>> OSPF Interface 1 # enable (Enable the transit area interface)
11. Attach the network interface to the transit area.
>> OSPF Interface 1 # ../if 2 (Select OSPF menu for IP interface 2)
>> OSPF Interface 2 # aindex 2 (Attach network to stub area index)
>> OSPF Interface 2 # enable (Enable the stub area interface)
12. Configure the virtual link.
13. The nbr router ID configured in this step must be the same as the router ID that was configured for
Switch A in step 2.
>> OSPF Interface 2 # ../virt 1 (Specify a virtual link number)
>> OSPF Virtual Link 1 # aindex 1 (Specify the transit area
for the virtual link)
>> OSPF Virtual Link 1 # nbr 10.10.10.1(Specify the router ID
of the recipient)
>> OSPF Virtual Link 1 # enable (Enable the virtual link)
14. Apply and save the configuration changes.
>> OSPF Interface 2 # apply (Apply all changes)
>> OSPF Interface 2 # save (Save all changes)
Other Virtual Link Options
• You can use redundant paths by configuring multiple virtual links.
• Only the endpoints of the virtual link are configured. The virtual link path may traverse multiple
routers in an area as long as there is a routable path between the endpoints.
Example 3: Summarizing routes
By default, ABRs advertise all the network addresses from one area into another area. Route
summarization can be used for consolidating advertised addresses and reducing the perceived
complexity of the network.
If the network IP addresses in an area are assigned to a contiguous subnet range, you can configure the
ABR to advertise a single summary route that includes all the individual IP addresses within the area.
The following example shows one summary route from area 1 (stub area) injected into area 0 (the
backbone). The summary route consists of all IP addresses from 36.128.192.0 through 36.128.254.255
except for the routes in the range 36.128.200.0 through 36.128.200.255.
