300-420 Question #99: Real Exam Question with Answer & Explanation

Question

Refer to the exhibit. An architect must design an IP addressing scheme for a multisite network connected via a WAN transit. The campus site must accommodate 12,000 devices and the branch sites must accommodate 1,000 devices. Which address scheme optimizes network device resources, contains convergence events to the different blocks of the network, and ensures future growth of the network?

Options

• ACampus: 10.0.0.0/18
• BCampus: 10.0.0.0/16
• CCampus: 10.0.0.0/10
• DCampus: 10.0.0.0/20

Explanation

To accommodate 12,000 devices for the campus while optimizing address space and allowing for future growth, a 10.0.0.0/18 network is the most appropriate IP addressing scheme.

Common mistakes.

• B. A /16 network provides 2^16 - 2 = 65,534 usable addresses, which is significantly more than 12,000 devices, leading to inefficient use of address space and larger routing tables.
• C. A /10 network provides 2^22 - 2 = 4,194,302 usable addresses, which is an extremely large block and highly inefficient for 12,000 devices, wasting vast amounts of address space.
• D. A /20 network provides 2^12 - 2 = 4,094 usable addresses. This is insufficient to accommodate 12,000 devices for the campus site.

Concept tested. IP subnetting and address space allocation

Reference. https://www.cisco.com/c/en/us/support/docs/ip/ip-addressing/13768-5.html

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