Huawei H12-831_V1.0 Exam - Topic 1 Question 89 Discussion

Question

On the network shown in the figure, IS-IS runs on R1, R2, R4, and R5, and the area ID is 49.0001. IS-IS runs on R3 and R6, and the area ID is 49.0002. The import-route isis level-2 into level-1 command is configured on R2.In AS 65000, R1, R3, R4, and R6 each establish iBGP peer relationships with R2 and R5. R2 and R5 are Route Reflectors (RRs), and R1, R4, R3, and R6 are clients.The iBGP peer relationships are established using Loopback0. The IP address of Loopback0 on each router is 10.0.X.X/32, and the router ID is 10.0.X.X, where X is the number of the router.R1 and R4 import the external route 192.168.1.0/24 to BGP through the import-route command, and R3 and R6 import the external route 192.168.2.0/24 to BGP through the import-route command.Which of the following statements are true?A. The route 192.168.2.0/24 in the routing table of R4 has two next hops.
B. The routing table of R1 contains two equal-cost default routes.
C. The routing table of R4 contains two equal-cost default routes.
D. The routing table of R1 contains the route 192.168.2.0/24.

Rodney · Accepted Answer

A) The route 192.168.2.0/24 in the routing table of R4 has two next hops.  (Correct)
R3 and R6 import 192.168.2.0/24 into BGP.
R2 and R5 (Route Reflectors) learn this route and reflect it to their clients (R1, R3, R4, R6).
R4 receives two valid paths to 192.168.2.0/24 via R2 and R5 (both iBGP peers).
Since both routes have the same BGP attributes and cost, they are installed as equal-cost paths in R4's routing table.
 Statement A is correct: The routing table of R4 has two next hops for 192.168.2.0/24. and D) The routing table of R1 contains the route 192.168.2.0/24.  (Correct)
R3 and R6 import 192.168.2.0/24 into BGP.
R2 and R5 (Route Reflectors) reflect this route to their iBGP peers, including R1.
Since R1 is an iBGP client of R2 and R5, it will receive 192.168.2.0/24 and install it in its routing table.
 Statement D is correct: The routing table of R1 contains the route 192.168.2.0/24.
Final Conclusion:
 A. The route 192.168.2.0/24 in the routing table of R4 has two next hops.
 B. The routing table of R1 does not necessarily contain two equal-cost default routes.
 C. The routing table of R4 does not necessarily contain two equal-cost default routes.
 D. The routing table of R1 contains the route 192.168.2.0/24.
Thus, the correct answers are: A, D.

Rodney · Answer

B) The routing table of R1 contains two equal-cost default routes.  (Incorrect)
In an IS-IS Level-1-2 setup, default routes are usually provided to Level-1 routers from an ABR (like R2).
However, the question does not mention that R1 is receiving two default routes or that it is in an equal-cost multipath (ECMP) scenario.
R1 may have only one default route, depending on route preference and cost.
 Statement B is incorrect: The routing table of R1 does not necessarily contain two equal-cost default routes.

Rodney · Answer

C) The routing table of R4 contains two equal-cost default routes.  (Incorrect)
Similar to R1, R4 is also a Level-1 router in IS-IS.
If R4 were receiving default routes from multiple ABRs (R2 and R5), then it could have equal-cost paths.
However, there is no indication that R4 is receiving two default routes in this scenario.
 Statement C is incorrect: The routing table of R4 does not necessarily contain two equal-cost default routes.