The value of the PROTOCOL field of the PPP protocol is 8021, what is the protocol represented?

Question

Options

• ALCP
• BIPCP
• CIP
• DIPX

• A
  15% (7)
• B
  74% (34)
• C
  4% (2)
• D
  7% (3)

Explanation

In PPP, the PROTOCOL field value 0x8021 is assigned to IPCP (Internet Protocol Control Protocol), which is the Network Control Protocol used to negotiate and configure IP layer settings before IP traffic can flow over a PPP link. IPCP handles parameters like IP address assignment between peers.

LCP (option A) is wrong because LCP uses protocol value 0xC021, not 0x8021 -- LCP operates at a lower layer to establish and configure the PPP link itself. Plain IP (option C) is wrong because IP datagrams are identified by 0x0021, not 0x8021 -- note that the leading 8 versus 0 is the key distinction. IPX (option D) uses a different protocol value entirely (0x002B for IPX data) and is unrelated to the 0x8021 value.

Memory tip: In PPP protocol field values, values beginning with 0x8 indicate Network Control Protocols (NCPs), which are control/negotiation protocols, while values beginning with 0x0 carry actual network layer data. Since IPCP is the control protocol for IP, and IP data itself is 0x0021, IPCP is the corresponding control counterpart at 0x8021 -- just swap the leading digit from 0 to 8.

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