The first IP option value begins at which byte offset within the IP header?

The first IP option value begins at which byte offset within the IP header?

• A. 10th byte offset
• B. 20th byte offset
• C. 30th byte offset
• D. 0th byte offset

Answer: (B)

In IPv4, the header has a fixed 20-byte portion. The IHL field tells how many 32-bit words the header uses, so if options are present, the header grows beyond 20 bytes and the options begin right after that fixed 20-byte base. Therefore, the first option value starts at the 20th byte offset within the header (counting from zero), which is after the initial 20 bytes. That’s why the 20th byte offset is the correct choice.

In IPv4, the header has a fixed 20-byte portion. The IHL field tells how many 32-bit words the header uses, so if options are present, the header grows beyond 20 bytes and the options begin right after that fixed 20-byte base. Therefore, the first option value starts at the 20th byte offset within the header (counting from zero), which is after the initial 20 bytes. That’s why the 20th byte offset is the correct choice.