Comprehensive and Detailed In-Depth Explanation:
To determine the cost value of the route 10.0.35.0/24 in the routing table of R1, let's analyze the possible shortest paths from R1 to R3 (which owns the 10.0.35.0/24 network) based on the given OSPF link costs:
* Path 1: R1 # R2 # R3
* R1 to R2: Cost = 20
* R2 to R3: Cost = 10
* Total Cost = 20 + 10 = 30
* Path 2: R1 # R4 # R3
* R1 to R4: Cost = 10
* R4 to R3: Cost = 10
* Total Cost = 10 + 10 = 20 # (Lowest cost path)
* Path 3: R1 # R5 # R3
* R1 to R5: Cost = 10
* R5 to R3: Cost = 10
* Total Cost = 10 + 10 = 20 # (Equal-cost path)
Final Calculation:
* The two best equal-cost paths (R1 # R4 # R3 and R1 # R5 # R3) have a cost of 20.
* Since OSPF supports equal-cost multi-path (ECMP) routing and maximum load-balancing 8 is enabled, OSPF will install both routes into the routing table with the same cost of 20.
* The path R1 # R2 # R3 has a higher cost (30) and will not be chosen.
Final answer: # 20 (Option C)
References:
* HCIP-Datacom-Advanced Routing & Switching Technology V1.0 - OSPF Route Calculation & Load Balancing
* OSPF Equal-Cost Multi-Path (ECMP) and Route Selection
* OSPF Fast Reroute (FRR) Mechanism