A company is using OSPF between its HQ location and a branch office.
HQ is assigned area 0 and the branch office is assigned area 1
The company purchases a second branch office, but due to circuit delays to HQ, it decides to connect the new branch office to the existing branch office as a temporary measure.
The new branch office is assigned to area 2
Which OSPF configuration enables all three locations to exchange routes?
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A. B. C. D.B.
In this scenario, the company has a hub-and-spoke network topology with HQ as the hub and the branch offices as spokes. OSPF is being used as the routing protocol between HQ and the branch office. The OSPF area assignment is HQ assigned area 0, branch office assigned area 1, and the new branch office assigned to area 2.
To enable all three locations to exchange routes, we need to ensure that there is end-to-end connectivity between all OSPF areas. OSPF does not allow for a direct connection between non-backbone areas, so we need to use one of the following methods to establish end-to-end connectivity between areas 0, 1, and 2:
Option A: The existing branch office must be configured as a stub area A stub area is an OSPF area that does not receive external routes from outside the area. By configuring the existing branch office as a stub area, we can prevent external routes from propagating into the branch office, thereby reducing the routing table size and conserving network resources.
However, this option does not provide end-to-end connectivity between areas 0, 1, and 2. It only limits the propagation of external routes into the existing branch office.
Option B: A virtual link must be configured between the new branch office and HQ A virtual link is a logical connection between two non-backbone areas through a backbone area. By configuring a virtual link between the new branch office (area 2) and HQ (area 0), we can establish end-to-end connectivity between the two non-backbone areas.
This option enables all three locations to exchange routes but requires a backbone area between areas 0 and 2. If there is no backbone area between areas 0 and 2, we cannot configure a virtual link.
Option C: A sham link must be configured between the new branch office and HQ A sham link is a logical connection between two OSPF routers through a non-OSPF network. By configuring a sham link between the new branch office and HQ, we can establish end-to-end connectivity between the two non-backbone areas.
This option enables all three locations to exchange routes but requires a non-OSPF network between the new branch office and HQ. Additionally, configuring a sham link is more complex than configuring a virtual link.
Option D: The new branch office must be configured as a stub area. Like Option A, configuring the new branch office as a stub area does not provide end-to-end connectivity between areas 0, 1, and 2. It only limits the propagation of external routes into the new branch office.
Conclusion: Option B or Option C is the correct answer, as they both provide end-to-end connectivity between areas 0, 1, and 2. However, the choice between the two options depends on the network topology and requirements. If there is a backbone area between areas 0 and 2, a virtual link is the preferred option. Otherwise, a sham link may be required.