The maximum number of IPv4 router addresses that can be listed in the record…
2017
The maximum number of IPv4 router addresses that can be listed in the record route (RR) option field of an IPv4 header is______.
Answer: 9 — Key insight: the IPv4 header is at most 60 bytes, so the options area is limited to 40 bytes. Base header = 20 bytes; maximum header = 60 bytes → options…
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Correct answer: 9
Key insight: the IPv4 header is at most 60 bytes, so the options area is limited to 40 bytes.
Base header = 20 bytes; maximum header = 60 bytes → options space = 40 bytes.
Record Route option format: 1 byte type + 1 byte length + 1 byte pointer = 3 bytes overhead, then 4 bytes per IPv4 address.
Let n be the number of addresses. 3 + 4n ≤ 40 → 4n ≤ 37 → n ≤ 9.25, so the maximum whole number of addresses is 9.
Answer: 9 router addresses can be listed in the Record Route option.
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