Analysis of the working principle of bridges and L2 switches-video notes

Analysis of the working principles of bridges and L2 switches-video notes: the working principles of bridges (L2 switches) and security threat hubs are rarely used. Pay attention to the knowledge of bridges. The characteristics of a bridge and a layer-2 switch conflict with each other. The advantage of using a CAM table to select two hosts can be sent simultaneously is also a security vulnerability.
What is a conflicting Domain? Although the hub organizes a network with a star structure, this so-called "star network" is actually a star that is connected to a physical environment. It is not a star on the Access Media Protocol (the Ethernet Access Media Protocol is CSMA/CD). From the perspective of the logic of the access media: any network that uses the hub to organize the network should be a conflicting network. The details are as follows: = abcd shares a CSMA/CD. =

= Routing Based on the MAC address table = CAM table = How CAM is formed --- MAC address self-learning (Bridge Function) =



= How to divide the conflicting domains = suppose there are 10 MB in total. Hub: only 2.5 M on average. Every bridge enjoys 10 M. = Network security threats faced by bridges and L2 switches the working principle of bridges and L2 switches is actually one thing. They all use MAC address self-learning to build MAC address tables, then, the data packet is routed through the MAC address table to improve the data forwarding speed of the bridge or L2 Switch, so as not to broadcast data to each port of the bridge or L2 Switch, security is also improved. However, the MAC address table of a bridge or L2 Switch has a capacity limit. The MAC address table is also called a CAM table, which is subject to the memory limit of a bridge or L2 Switch, generally, the capacity of a CAM table can contain thousands to tens of thousands of MAC records, which may vary depending on the brand and grade of different switches. If these CAM tables are full of attacked intruders in a few seconds, a switch CAM table Overflow Event will be generated, and normal CAM cannot be learned by the switch, the switch cannot select the corresponding link between the normal MAC address and the port. packets entering the switch will be broadcast to each port. Then the switch and the hub will become the same network device, intruders can successfully listen on all data of a vswitch as long as they connect their computers to any port of the vswitch. L2 switches are faster than bridging switches. The working principle is the same. Network security threats faced by bridges and L2 switches =