Your area boarder router (ABR) receives type 1, 2, and 5 link-state advertisements (LSAs) from a nonbackbone area. What would the ABR do with the information learned from the nonbackbone area?
Click on the arrows to vote for the correct answer
A. B. C. D.C
In OSPF (Open Shortest Path First), the ABR (Area Border Router) is a router that connects two or more areas within an OSPF network. When an ABR receives LSAs (Link-State Advertisements) from a non-backbone area, it performs certain operations depending on the type of LSAs received. The type of LSAs can be identified from the LSA header.
Type 1 LSAs are generated by each router within an area and describe the router's directly connected links within that area. Type 2 LSAs are generated by the ABR to describe the networks that are reachable within the non-backbone areas. Type 5 LSAs are generated by the ASBR (Autonomous System Border Router) to describe external routes, such as those learned from other routing protocols or static routes.
Now let's analyze each answer option one by one:
A. It will generate type 2 and 3 LSAs and flood type 5 LSAs to the backbone area This option is incorrect because the ABR does not generate type 3 LSAs when it receives LSAs from a non-backbone area. Type 3 LSAs are generated by the ABR itself to describe the networks that are reachable within its attached areas.
B. It will generate only type 3 LSAs and flood only type 5 LSAs to the backbone area This option is also incorrect because the ABR does not generate type 3 LSAs when it receives LSAs from a non-backbone area. Type 3 LSAs are generated by the ABR itself to describe the networks that are reachable within its attached areas.
C. It will generate type 3 and 4 LSAs, and flood type 5 LSAs to the backbone area This option is incorrect because the ABR does not generate type 4 LSAs when it receives LSAs from a non-backbone area. Type 4 LSAs are generated by the ABR itself to describe the ASBRs within an area.
D. It will generate only type 4 LSAs and flood only type 5 LSAs to the backbone area This option is incorrect because the ABR does not generate type 4 LSAs when it receives LSAs from a non-backbone area.
Therefore, none of the answer options is correct. In reality, when an ABR receives type 1, 2, and 5 LSAs from a non-backbone area, it generates type 3 LSAs based on the information learned from those LSAs and floods type 3 and 5 LSAs to the backbone area. The type 2 LSAs are not flooded to the backbone area because they are already generated by the ABR itself based on the information it learned from the non-backbone area.