Huawei Certified ICT Professional – Data Center Network (HCIP-DCN) — Question 22

On an OSPF network, an algorithm is used to prevent loops within an area, but loops may occur between areas. Therefore, OSPF defines a loop prevention mechanism for inter-area routes. Which of the following statements are true about the loop prevention mechanism? (Choose all that apply.)

Answer options

• A. An ABR cannot inject Type 3 LSAs that describe routes to a network segment in an area back to the same area.
• B. Inter-area routes need to be forwarded through area 0.
• C. Inter-area routes cannot be directly transmitted between non-backbone areas.
• D. All non-backbone areas must be directly connected to area 0.

Correct answer: A, B, D

Explanation

Option A is correct because an ABR is designed to prevent the injection of Type 3 LSAs back into the same area to avoid routing loops. Option B is true since inter-area routes must traverse area 0, which is the backbone of the OSPF network. Option D is also correct because a fundamental design of OSPF requires that all non-backbone areas must connect directly to area 0 to ensure proper inter-area routing. Option C is incorrect as it misrepresents the routing capabilities; while non-backbone areas cannot route directly to each other, they can communicate through area 0.