Chapter 8. Securing Layer 2 Technologies

This chapter covers the following subjects:

• VLAN and trunking fundamentals

• Spanning-Tree fundamentals

• Common Layer 2 threats and how to mitigate them

We often take for granted Layer 2 in the network because it just works. Address Resolution Protocol (ARP) and Layer 2 forwarding on Ethernet are all proven technologies that work very well. This certification, the CCNA Security, was built with the presumption that candidates would have a CCNA in route/switch or equivalent knowledge. With this knowledge, your understanding of the details about VLANs, trunking, and inter-VLAN routing is presumed. However, so that you absolutely understand these fundamental concepts, this chapter begins with a review. ...

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