Overview:
Catalyst switch port security is so often recommended. This is because of a couple of important points:
- There are many attacks that are simple to carry out at Layer 2.
- There tends to be a gross lack of security at Layer 2.
- Port Security can guard against so many different types of attacks. Just a few to mention are MAC flooding, MAC spoofing, and rouge DHCP and APs.
There are often two main points that are confusing for engineers about this feature, however.
1.What is Sticky Learning and how does it work?
2.What is the difference between the different violation modes and how can I remember them?
Port Security Sticky Learning:
Sticky learning is a convenient way to set static MAC address mappings for MAC addresses that you allow on your network. What you do is confirm that the correct devices are connected to the appropriate switch ports. You then turn on sticky learning and the port security feature itself, for example:
switchport port-security maximum 2
switchport port-security mac-address sticky
switchport port-security
Now what happens is the 2 MAC addresses for the two devices you trust (perhaps an IP Phone and a PC) are dynamically learned by the switch. The switch automatically writes static port security entries in the running configuration for those two devices. All you have to do is save the running configuration, and poof, you are now configured with the powerful static MAC port security feature.
Please note that it is easy to forget to actually turn on port security after setting the parameters. This is what the third line is doing in the configuration above. Always use your show port-security commands to confirm you remembered this important step of the process!
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