Which of the following is FALSE regarding the 16-bit public autonomous system numbers?

Question

Options

• AThey are allocated to the RIRs by ICANN/IANA.
• BThey are used when connecting ASs on the Internet.
• CThey range from 1 to 56319.
• DThey are assigned by the ISPs for enterprise networks.

• A
  6% (3)
• B
  4% (2)
• C
  2% (1)
• D
  87% (41)

Explanation

Option D is FALSE because public Autonomous System Numbers (ASNs) are not assigned by ISPs - they are assigned by Regional Internet Registries (RIRs) such as ARIN, RIPE NCC, APNIC, LACNIC, and AFRINIC. Enterprises or organizations that need a public ASN must apply to their regional RIR directly.

Why the other options are TRUE (and therefore not the answer):

• A is true: IANA (under ICANN) is responsible for the global IP address and ASN space, and it allocates blocks of ASNs to the five RIRs for regional distribution.
• B is true: Public 16-bit ASNs are used by BGP (Border Gateway Protocol) to uniquely identify autonomous systems exchanging routing information on the Internet.
• C is true per the question's context: The public 16-bit ASN range runs from 1 to 56,319 (the remainder of the 16-bit space is reserved for private use or other purposes).

Memory tip: Think of the hierarchy - IANA → RIRs → Organizations. ISPs are customers of RIRs, not distributors of ASNs. If you remember "RIRs register, ISPs route," you won't confuse the two roles on exam day.

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