Which one of the following fields of an IP header is NOT modified by a typical IP router?
(A) Checksum
(B) Source address
(C) Time to Live (TTL)
(D) Length


Answer: (B)

Explanation: Length and checksum can be modified when IP fragmentation happens. Time To Live is reduced by every router on the route to destination.

Only Source Address is what IP address can not change SO B is the answer.

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