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To conclude this chapter, a list of best practices is presented here for implementing, managing, and maintaining secure Layer 2 network:
Manage the switches in a secure manner. For example, use SSH, authentication mechanism, access list, and set privilege levels.
Restrict management access to the switch so that untrusted networks are not able to exploit management interfaces and protocols such as SNMP.
Always use a dedicated VLAN ID for all trunk ports.
Be skeptical; avoid using VLAN 1 for anything.
Disable DTP on all non-trunking access ports.
Deploy the Port Security feature to prevent unauthorized access from switching ports.
Use the Private VLAN feature where applicable to segregate network traffic at Layer 2.
Use MD5 authentication where applicable.
Disable CDP where possible.
Prevent denial-of-service attacks and other exploitation by disabling unused services and protocols.
Shut down or disable all unused ports on the switch, and put them in a VLAN that is not used for normal operations.
Use port security mechanisms to provide protection against a MAC flooding attack.
Use port-level security features such as DHCP Snooping, IP Source Guard, and ARP security where applicable.
Enable Spanning Tree Protocol features (for example, BPDU Guard, Loopguard, and Root Guard).
Use Switch IOS ACLs and Wire-speed ACLs to filter undesirable traffic (IP and non-IP).
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