What is the purpose of the IPv4 Version field?

• A. It identifies the protocol version and must be 4 for IPv4
• B. It identifies the packet’s destination address
• C. It indicates the header checksum
• D. It specifies the total length

Answer: (B)

The Version field in an IPv4 header tells devices which version of the Internet Protocol this packet uses and how to interpret the rest of the header. It is 4 bits long, and for IPv4 packets its value must be 4. This small field lets routers and hosts distinguish IPv4 from other IP versions (like IPv6) so they apply the correct parsing rules.

This field does not carry the destination address—that’s in the Destination Address field. It also isn’t the place for the header checksum or the total length; those have their own separate fields (the checksum and the total length fields, respectively). So the purpose of the Version field is to identify the protocol version and indicate that the packet is IPv4, enabling proper processing.