What is the IP protocol number for UDP?

What is the IP protocol number for UDP?

• A. 6
• B. 8
• C. 19
• D. 17

Answer: (D)

In IP headers, there is a field that tells the network stack which transport-layer protocol follows the IP payload. UDP is identified by the value 17 in that field. So when the IP header shows the protocol (or Next Header in IPv6) as 17, it means the payload should be processed as UDP. This numbering is defined by IANA and is shared across IPv4 and IPv6. For reference, 6 corresponds to TCP and 1 to ICMP, with other numbers mapping to additional protocols.

In IP headers, there is a field that tells the network stack which transport-layer protocol follows the IP payload. UDP is identified by the value 17 in that field. So when the IP header shows the protocol (or Next Header in IPv6) as 17, it means the payload should be processed as UDP. This numbering is defined by IANA and is shared across IPv4 and IPv6. For reference, 6 corresponds to TCP and 1 to ICMP, with other numbers mapping to additional protocols.