Ccna routing and Switching Complete Study Guide

Introduction to Cisco IOS IPsec

Simply put, IPsec is an industry-wide standard framework of protocols and algorithms that 

allows for secure data transmission over an IP-based network and functions at the layer 3 

Network layer of the OSI model.

Did you notice I said IP-based network? That’s really important because by itself, IPsec 

can’t be used to encrypt non-IP traffic. This means that if you run into a situation where 

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Chapter 21 

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  Wide Area Networks

you have to encrypt non-IP traffic, you’ll need to create a Generic Routing Encapsulation 

(GRE) tunnel for it (which I explain later) and then use IPsec to encrypt that tunnel!