A Cisco Meraki MX security appliance is trying to route a packet to the destination IP address of 172.18.24.12. Which routes contained in its routing table does it select?

Question

Options

• AAuto VPN route 172.18.0.0/16
• Bstatic route 172.16.0.0/12
• Cnon-Meraki VPN route 172.18.24.0/24
• Ddirectly connected 172.18.16.0/20

• A
  4% (2)
• B
  5% (3)
• C
  75% (42)
• D
  16% (9)

Explanation

Option C wins because routers always select the most specific matching route - the one with the longest prefix (subnet mask). All four routes technically contain 172.18.24.12 within their address range, but 172.18.24.0/24 has a 24-bit prefix, making it more specific than option A (172.18.0.0/16), option B (172.16.0.0/12), and option D (172.18.16.0/20). Options A, B, and D are not wrong about matching the destination - they are simply less specific, and the longest prefix match (LPM) rule means the router always prefers the narrower, more targeted route regardless of its type (static, VPN, directly connected, etc.).

Memory tip: Think of it like a mailing address - "123 Main St, Apt 4B" wins over just "123 Main St," which wins over just "Main St." The more detail in the route, the higher its priority. When you see a routing question, count the prefix bits and pick the biggest number.

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