Comprehensive and Detailed In-Depth Explanation:
Understanding the BGP Network Topology in the Question:
* EBGP Peering & Route Distribution
* Each router forms EBGP peer relationships with directly connected neighbors.
* BGP learns and propagates routes via EBGP neighbors.
* R1 and R4 advertise the static route 192.168.1.0/24 into BGP.
* Effect of the aggregate 192.168.1.0/16 detail-suppressed Command on R2
* R2 performs BGP route aggregation, summarizing 192.168.1.0/24 into a larger 192.168.1.0/16 route.
* The detail-suppressed option hides the more specific 192.168.1.0/24 prefix when advertising routes.
* As a result, R2 does not advertise the specific 192.168.1.0/24 route to its neighbors.
Route Selection and Traffic Flow Analysis:
* R1 and R4 originate 192.168.1.0/24 and advertise it via BGP.
* R2 does not advertise the 192.168.1.0/24 route because of the detail-suppressed command.
* R3 cannot learn the specific route from R2, so it must choose an alternative path via R5.
* R5 learns 192.168.1.0/24 from R1 and advertises it to R3.
* Thus, the best available path for R3 to reach 192.168.1.0/24 is R3 # R5 # R1.
# Correct Path: R3 # R5 # R1
Checking Each Option:
# Option A: R3 # R5 # R1 (Correct)
* R3 learns 192.168.1.0/24 from R5, and R5 forwards traffic to R1, which has the static route.
# Option B: R3 # R2 # R1 (Incorrect)
* R2 does not advertise 192.168.1.0/24 due to route summarization (detail-suppressed), so R3 cannot use R2 as the next hop.
# Option C: R3 # R6 # R5 # R1 (Incorrect)
* This is an unnecessary detour.
* R3 has a direct EBGP connection with R5, so it will use the shortest path (R3 # R5 # R1) instead of going through R6.
# Option D: R3 # R5 # R4 (Incorrect)
* R3 prefers the shortest AS path to reach 192.168.1.0/24.
* Since R1 and R4 both advertise the route, R3 will prefer the route via R5 to R1 rather than R4.
Final Conclusion:
# A. The correct path for traffic from R3 to 192.168.1.0/24 is R3 # R5 # R1.
Thus, the correct answer is: A.