What is the maximum number of IP addresses that can be stored using the Record Route option?

What is the maximum number of IP addresses that can be stored using the Record Route option?

• A. 9 time stamps
• B. 5 time stamps
• C. 12 time stamps
• D. 16 time stamps

Answer: (A)

Record Route stores a list of router addresses in the IPv4 options field, and that field is limited to 40 bytes in total. The option header itself uses 3 bytes (type, length, pointer), and each stored address takes 4 bytes. So you can fit floor((40 − 3) / 4) = floor(37 / 4) = 9 addresses. That means up to nine entries can be recorded, which some questions refer to as time stamps. The others listed would require more space than the 40-byte limit allows.

Record Route stores a list of router addresses in the IPv4 options field, and that field is limited to 40 bytes in total. The option header itself uses 3 bytes (type, length, pointer), and each stored address takes 4 bytes. So you can fit floor((40 − 3) / 4) = floor(37 / 4) = 9 addresses. That means up to nine entries can be recorded, which some questions refer to as time stamps. The others listed would require more space than the 40-byte limit allows.