I would like to understand the principle of the switch and how it differs from the bridge. The question arose due to completely different definitions on different sites that are contradictory.

  1. Do I understand correctly that a switch is a device with several ports, which, unlike a hub, can transmit a signal to a specific port (a hub can only repeat to all ports) thanks to the routing table?

  2. Then I don’t understand how training takes place at the switchboard (routing table), because until each of the ports has data sent, the table is not full? This means that until the table is full, all the computers on the network will be able to see what I wanted to transfer to only one specific computer (this seems to be unsafe)?

  3. Do I understand correctly that the hub works as an analog device - the signal that it transmitted it repeated and that's it? But the switch is like a digital-analog one - it first digitally divided the packets into the packets, and then by analogy (cable) sent it to the correct port (or to all ports, if training is going on)?

  4. How does a bridge differ from a switch?

    2 answers 2

    1. Yes. Only this is not quite the routing table;
    2. Read how the ARP protocol works;
    3. Yes. Like that
    4. They connect networks at different levels. The bridge - a more complicated piece of hardware - can make one IP network with a single address space from different networks (including remote ones)

    The bridge connects the networks at the second level. But the traffic between the "ends" of the bridge can go through any levels. The bridge analyzes the network and collects a table of MACs noting which physical network they belong to. Receiving a packet analyzes the address of the recipient. If this address does not belong to the network from which the packet came, the bridge sends it to another interface. If the receiver and the sender are in the same network, the bridge ignores the packet. In modern networks, probably the most common application in Wi-Fi access points.

    • 4. Can I be more specific? The switch can not make one IP network with a single address space? - Pavel Igorev
    • And what does connecting networks at different levels mean? - Pavel Igorev
    • It cannot, since it does not work with IP addresses, but with MAC addresses. - HasmikGaryaka
    • Then how does the bridge differ from the router, if it can work with ip too? - Pavel Igorev
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      How a bridge differs from a router A router provides packet transmission between different IP subnets — while they may exist on the same physical network (segment) or different ones. The bridge connects two different segments, whose IP subnets are the same or different (and in one of the segments, there must be a router between these IP subnets). - Akina

    The switch operates at the second level of the OSI model (MAC sublayer), since it analyzes the MAC addresses inside packet 10 (Fig. enter image description here .). Naturally, it performs the functions of the first level.

    Routers work at the third level of the OSI model, since they analyze not only the MAC addresses of the packet, but also the IP addresses, that is, they penetrate deeper into the encapsulated packet. enter image description here

    The network segmentation task, i.e. dividing users into groups (segments) in accordance with their physical placement in order to reduce the number of clients competing for bandwidth was solved using a device called a bridge. The bridge was developed by Digital Equipment Corporation (DEC) in the early 1980s and was a data link layer device (OSI model (usually dual port)) designed to unite network segments. Unlike a hub, the bridge not only forwarded data packets from one segment to another, but analyzed and transmitted them only if such a transfer was really necessary, that is, the address of the destination workstation belonged to another segment. Thus, the bridge isolated the traffic of one segment from the traffic of another, reducing the collision domain and increasing the overall network performance.

    However, the bridges were effective only as long as the number of workstations in the segment remained relatively small. As it increased, there was an overload in the networks (overflow of receiving buffers of network devices), which led to packet loss.

    The increase in the number of devices connected to the network, the increase in the power of the processor of workstations, the emergence of multimedia applications and client-server applications required more bandwidth. In 1990, in response to these growing demands, Kalpana launched the first switchboard on the market, called the EtherSwitch.

    LAN switch

    The switch was a multiport bridge and also functioned on the data link layer of the OSI model. The main difference between the switch and the bridge was that it could simultaneously establish several connections between different pairs of ports. When a packet was transmitted through a switch, a separate virtual (or real, depending on the architecture) channel was created in it, through which data was sent directly from the source port to the destination port with the maximum speed possible for the technology used. This principle of operation has been called "microsegmentation". Thanks to microsegmentation, the switches were able to operate in full duplex mode, which allowed each workstation to simultaneously transmit and receive data using the entire bandwidth in both directions. The workstation did not have to compete for bandwidth with other devices, resulting in no collisions and increased network performance.

    • 2
      If you use other people's texts, mark the text as quotes and put links to the source. Otherwise it is plagiarism. - tutankhamun
    • 2
      And better in your own words, and then stupidly copied and a lot of water. - Pavel Igorev