What are the roles and differences between hubs, switches, and routers?

The hub does not have a switch** function, the information received from one port is broadcast from all other ports, and the hub only acts as a signal amplification.

Strictly speaking, a switch has only Layer 2 functions, which are based on MAC address packets. After receiving packets from a port, query the port corresponding to the destination MAC address and send the packet from that port. At the same time, write the source MAC address of the packet to the MAC address of the port where the packet is received.

This is because it already knows that the host corresponding to the source MAC is connected to the port where the packet was received. In the future, when receiving packets destined for MAC address, only the port that receives the packets is sent.

The router looks up the routing table based on the IP address ** packet and sends it from the lookup to the outbound interface of the router. The routing table is calculated by routing protocols such as OSPF.

Many of today's switches also have routing functions, so such switches are called routing switches. To put it simply, a routing switch is a simple collection of routers and switches that can use both MAC address packets and IP packets.

Hub + Switch = Router.

Therefore, routers are very expensive, and Internet cafes and small and medium-sized enterprises do not need to use hubs or switches for routing.

1. The role of the router: let multiple computers share network resources through a broadband; 2. Hub: When the socket of the router is insufficient, the hub serves as its branch and has the function of amplifying the signal; 3. Switch:

Its function is basically the same as that of the hub, but the clients of the hub cannot access each other, that is, there are no online neighbors, while the switch can allow the clients connected to it to achieve mutual access and have online neighbors;

A switch is the equivalent of a combination of multiple hubs. There are more interfaces than multi-hubs. If it is an advanced point switch (Cisco class), it is more powerful.

Routers are routers. Routing, is to find the address you want to access.

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(1) Different levels of work.

The original switches were designed to work at the data link layer, which is Layer 2, of the OSI RM Open Architecture, while the routers were designed to work at the network layer of the OSI model from the beginning. Since the switch works at the second layer of the OSI (data link layer), its working principle is relatively simple, while the router works at the third layer of the OSI (network layer), which can get more protocol information and the router can make more intelligent decisions.

2) The data is based on different objects.

The switch uses the physical address or MAC address to determine the destination address of the data. Routers, on the other hand, use the ID numbers (i.e., IP addresses) of different networks to determine the address of the data**. IP addresses are implemented in software and describe the network on which the device is located, and sometimes these Layer 3 addresses are also called protocol addresses or network addresses.

MAC addresses are usually hardware built-in, assigned by the NIC manufacturer, and solidified into the NIC and generally cannot be changed. IP addresses, on the other hand, are usually assigned automatically by the network administrator or the system.

3) The traditional switch can only divide the collision domain, but cannot divide the broadcast domain; Whereas, routers can split the broadcast domain.

The network segments connected by the switch still belong to the same broadcast domain, and broadcast packets are propagated across all network segments connected by the switch, causing traffic congestion and security breaches in some cases. The network segments connected to the router are assigned different broadcast domains, and the broadcast data does not pass through the router. Although switches above Layer 3 have VLAN functions and can also divide broadcast domains, they cannot communicate with each other, and routers are still required to communicate between them.

4) The router provides the service of a firewall.

The router only transmits packets at a specific address, and does not transmit packet delivery that does not support routing protocols and the transmission of packets from unknown destination networks, thus preventing broadcast storms.

Hubs and switches are almost the same, both have data exchange functions, routers have data exchange and routing functions, routers are Layer 3 devices, switches are Layer 2, and hubs are layer 1.