From the course: Cisco CCNA (200-301) Cert Prep: 3 Security, Automation, and Programmability

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Port security

Port security

From the course: Cisco CCNA (200-301) Cert Prep: 3 Security, Automation, and Programmability

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Port security

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- [Instructor] Layer two security doesn't have, a one size fits all solution, there isn't an easy button for it. Rather, it's a layering of multiple techniques to achieve as much protection as is required. I'll start by discussing a feature known as Port Security. In essence, it limits the number of MAC addresses and even which MAC addresses are allowed to send inbound packets on a switch port. Limiting the number of MAC addresses, can prevent attacks like DHCP starvation, where tens or hundreds of MACs, will show up on a single interface. When enabled on a port by default, only a single MAC address will be learned, incoming on that port. And the logic is first come first served. This means if you have multiple MAC addresses, leaving off this port, whoever sends a packet first wins. The default violation mode is to shut down the port, if additional MACs arrive. I always adjust this behavior as seen below. While port security can be applied to a trunk port, I wouldn't recommend it…

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