On the difference and use of switches, hubs and routers

On the difference and use of switches, hubs and routers

Recently, I have seen many people asking what switches, hubs, and routers are, how they function, and what is the difference. The author simply answers these questions.
Let me talk about HUB first, which is the hub. Its role can be simply understood as connecting some machines to form a local area network. The switch (also known as a switching hub) is basically the same as a hub. However, there is a difference in performance between the two: the hub uses a shared bandwidth working method, and the switch is exclusive to the bandwidth. In this way, when there are many machines or a large amount of data, the two will be more obvious. The router is obviously different from the above two. Its role is to connect different network segments and find the most suitable path for data transmission in the network. It can be said that individual users generally have little demand. The router is generated after the switch, just like the switch is generated after the hub, so the router and the switch also have a certain connection, not two completely independent devices. The router mainly overcomes the deficiency that the switch cannot route and forward data packets.

In general, the main differences between routers and switches are reflected in the following aspects:

(1) Different working levels

The original switch was working at the data link layer of the OSI / RM open architecture, which is the second layer, and the router was designed to work at the network layer of the OSI model from the beginning. Since the switch works at the second layer (data link layer) of OSI, its working principle is relatively simple, while the router works at the third layer (network layer) of OSI, can get more protocol information, the router can Smarter forwarding decisions.

(2) Different objects based on data forwarding

The switch uses the physical address or MAC address to determine the destination address for forwarding data. The router uses the ID numbers (ie, IP addresses) of different networks to determine the data forwarding address. IP addresses are implemented in software and describe the network where the device is located. Sometimes these third layer addresses are also called protocol addresses or network addresses. The MAC address is usually carried by the hardware, and is assigned by the network card manufacturer, and has been solidified into the network card, and generally cannot be changed. The IP address is usually automatically assigned by the network administrator or system.

(3) Traditional switches can only divide conflict domains, not broadcast domains; routers can divide broadcast domains

The network segments connected by the switch still belong to the same broadcast domain, and broadcast packets will be propagated on all network segments connected by the switch, which in some cases may cause communication congestion and security holes. The network segments connected to the router will be allocated into different broadcast domains, and the broadcast data will not pass through the router. Although switches above the third layer have the VLAN function and can also divide the broadcast domain, the communication between the sub-broadcast domains is not possible, and the communication between them still requires a router.

(4) The router provides firewall services

The router only forwards data packets at a specific address, and does not transmit data packets that do not support routing protocols or unknown target network packets, thereby preventing broadcast storms.

The switch is generally used for LAN-WAN connection. The switch belongs to the bridge and is a device at the data link layer. Some switches can also implement the third layer of switching. The router is used for WAN-WAN connection, which can solve the forwarding of packets between heterosexual networks, acting on the network layer. They just accept incoming packets from one line and forward them to another line. These two lines may belong to different networks and use different protocols. In comparison, routers are more powerful than switches, but they are relatively slow and expensive. Layer 3 switches have both the wire-speed forwarding capability of switches and the router's good control functions, so they are widely used.

At present, more personal broadband access methods are ADSL, so I will briefly explain the ADSL access. Most of the ADSL cats that are purchased now have routing functions (many times the manufacturer shields the routing function at the factory, because most of the telecommunications installation does not enable the routing function, enable DHCP. Turn on the ADSL routing function) A few can be used by ADSL itself, if you have more computers, you only need to buy one or more hubs or switches. Considering that the price difference between the hub and the switch is very small today, it is not a special reason, please buy a switch. There is no need to pursue high prices, because the homogenization of products is very serious now, and my cheapest switch now has no problems. Give you a reference quotation, it is recommended that you buy an 8-port to meet the expansion needs, the general price is about 100 yuan. Connect the switch, and then connect all the computers to the switch. The only thing left to do is to insert the network cable of each machine into the interface of the switch and the cat's network cable into the uplink interface. Then set the routing function, DHCP, etc., you can share the Internet.

After reading the above explanation, readers should have some understanding of switches, hubs, and routers. The current use is mainly based on the combination of switches and routers. The specific combination can be determined according to the specific network conditions and needs.

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