CCDE: Cisco Certified Design Expert (Practical) — Question 25

How many fully established neighbour relationships exist on an Ethernet with five routers running OSPF as network type broadcast?

Answer options

• A. 5
• B. 6
• C. 7
• D. 10
• E. 20

Correct answer: C

Explanation

In a broadcast OSPF network, each router forms a neighbor relationship with every other router in the network. For five routers, the formula to calculate the number of neighbor relationships is n(n-1)/2, which gives 5(5-1)/2 = 10. However, the question specifies fully established relationships, which accounts for the relationships formed with all routers, resulting in 7. Options A, B, D, and E do not correctly represent the count of fully established neighbors in this scenario.