Network security is only as strong as the weakest link, because a single weak point if exploited successfully would be enough for an intruder. That weak link can be the data link layer or layer 2 of the OSI reference model. We can secure the posterior of our network protecting it from external threats but it is equally important to secure the interior of the network as several threats actually originate from the inside. Like routers, Cisco switches too have their own set of network security requirements.