Which of the following descriptions about the Options field in the DHCP message are correct? (Multiple choice)

Question

Options

• AOption 82 can contain up to 256 Sub-Options
• BThe Options field consists of three parts: Type, Length and Value
• COption 82 contains not only the MAC address of the relay device.
• DOption 82 is called the relay agent information option, which records the VLAN ID of the switch port connected to the DHCP client

• A
  23% (9)
• B
  78% (31)

Explanation

B is correct because DHCP options follow the standard TLV (Type-Length-Value) encoding: a 1-byte Type code identifies the option, a 1-byte Length specifies how many bytes of data follow, and the Value carries the actual content - this structure applies to all DHCP options, not just Option 82.

C and D are correct because Option 82 (the Relay Agent Information Option) is inserted by a DHCP relay agent (typically a Layer 3 switch) and carries sub-options beyond just a MAC address - Sub-option 1 (Circuit ID) encodes information like the VLAN ID and port of the client-facing interface, while Sub-option 2 (Remote ID) identifies the relay agent itself using various identifiers.

A is wrong because Option 82 does not support "up to 256" sub-options; the sub-option code field is 1 byte (values 0–255), meaning at most 255 usable codes, and only a small handful are actually defined by IANA - so the number 256 is both technically inaccurate and practically misleading.

Memory tip: Think of Option 82 as the relay agent's "business card" - it tells the DHCP server where the client is (Circuit ID = port/VLAN) and who forwarded the request (Remote ID = relay identity), and like all DHCP options, it's always written in Type-Length-Value format (TLV).

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