In order to establish a secure connection between headquarters and a branch office over a public network, the router at each location should be configured to use IPSec (Internet Protocol Security) in ______ mode.

A.
Secure

B.
Tunnel

C.
Transport

D.
Data link

Explanation:
IPSec provides secure authentication and encryption of data and headers. IPSec can work in Tunneling mode or Transport mode. In Tunneling mode, the data or payload and message headers are encrypted. Transport modes encrypts only the payload.
Reference: Security + (SYBEX) page 127