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CISSP study material · question 277 of 500

Where does the ESP header sit in transport mode compared with tunnel mode?

  1. In both modes immediately after the link layer header, differing only in key material.
  2. In transport mode before the IP header; in tunnel mode after it.
  3. In transport mode inside the payload; in tunnel mode inside the trailer.
  4. In transport mode after the IP header and before the next layer protocol header; in tunnel mode before a complete encapsulated IP header.
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Answer: D. In transport mode after the IP header and before the next layer protocol header; in tunnel mode before a complete encapsulated IP header.

RFC 4303 places the ESP header after the IP header and before the next layer protocol header in transport mode, and before an encapsulated IP header in tunnel mode.

Source: RFC 4303 (IETF) — RFC 4303 > 1. Introduction

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