OSPF Virtual Link - Repairing Partitioned Area 0 - Learn Cisco

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OSPF Virtual Link - Repairing Partitioned Area 0



Task 1
You have been called as a network consultant to configure OSPF Area 0 between R5 and SW3 in XYZ Enterprises. 

Task 2
After several months, your company acquires XYZ Enterprises. Without changing area 0 between R5 and SW3, enable OSPF connectivity with the rest of the OSPF domain. Use OSPF capability to connect partitioned backbone areas.

Questions
Try to answer the following questions:
  1. Is there an alternative way of doing it without utilizing OSPF capability?
Lab Solution

Solution configuration can be accessed below; solution contains task 1 and task 2 (if you want to save it, click the link, then go to File-->Download):
https://drive.google.com/file/d/0BwE5C95tpjZOejU0VVVVRmlWYkU/edit?usp=sharing


Task 1
You have been called as a network consultant to configure OSPF Area 0 between R5 and SW3 in XYZ Enterprises.

R5 Config:
!
router ospf 1
 network 172.16.59.5 0.0.0.0 area 0
!

SW3 Config:
!
router ospf 1
 network 172.16.59.9 0.0.0.0 area 0
!

Pic. 2 - SW3 OSPF Neighbor and OSPF Routing Table.


Note!
Since Area 0 is now partitioned, SW3 is not learning all OSPF prefixes (only what R5 is advertising as local networks). Now, R5 complains about mismatched area ID and prompts for virtual-link creation.

Task 2
After several months, your company acquires XYZ Enterprises. Without changing area 0 between R5 and SW3, enable OSPF connectivity with the rest of the OSPF domain. Use OSPF capability to connect partitioned backbone areas.

R4 Config:
!
router ospf 1
 area 45 virtual-link 10.0.5.5
!

R5 Config:
!
router ospf 1
 area 45 virtual-link 10.0.4.4
!


Pic. 3 - R4 to R5 Connection with OSPF Virtual-Link.


Pic. 4 - SW3 Current Routing Table.


Now, SW3 has full connectivity to OSPF domain.

Study Drill

The lab stipulates that we should use OSPF capability to create connection between partitioned areas 0. If there was no stipulation like this, we could also use GRE tunnel can be used to accomplish the same goal. Try to do it on your own.

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