Describes the classification of HUB and Its Application in daily work.

A hub is a connection device connected to multiple computers or other devices in a computer network. It is the smallest unit for centralized network management. A hub is a collection of branches, just like the trunk of a tree. Many types of networks rely on hubs to connect devices and distribute data to different network segments. The HUB is basically a shared device, and its essence is a repeater. It mainly provides signal amplification and transfer functions. It distributes all signals received by a port to all ports. Some hubs reinforce the weak signal before distribution and then send it again. Some hubs arrange the signal timing to provide synchronous data communication between all ports.

HUB is mainly used for Star Ethernet, which is the most economical solution to direct the server to the desktop. The HUB network is flexible. It is a star node in the network and centrally manages the workstations connected to the nodes, so that the problematic workstation does not affect the normal operation of the entire network, in addition, users can join and exit freely.

If you want to create a star network with more than two hosts (including servers), you need a hub. Of course, you can also add NICs to the server, which is a standard 24-port hub.

1. Types of HUB

There are multiple types of hubs. Each type has specific functions and provides services of different levels. Based on the bandwidth of the bus, the HUB is divided into 10 M, M, and 10 M/M adaptive three types. If the configuration form is different, it can be divided into three types: Independent, modular, and stacked; according to the number of ports, there are eight, 16, and 24 ports. According to the working method, there are two types: intelligent and non-intelligent. Currently, the HUB is basically a combination of the first three categories, such as the 10 M/M Adaptive intelligence and stackable HUB that we often see in advertisements.

There is a general significance for Distinguishing Based on the working method. Four types can be further divided: passive hub, active hub, smart hub, and switch hub.

1. passive HUB)

A passive hub only connects multiple network media and allows signal passing without any processing. It cannot improve network performance or help detect hardware errors or performance bottlenecks, simply receiving data from a port and distributing data through all ports is the easiest thing a hub can do. A passive hub is an entry-level device for Star Ethernet.

A passive hub usually has a 10Base-2 port and some RJ-45 interfaces. The 10Base-2 connector can be used to connect the trunk. Some hubs also have AUI ports that can be connected to the transceiver to create a network trunk.

2. Active active HUB)　

The active hub has all the performance of the passive hub and can monitor data. In the Ethernet storage and forwarding function, the active hub checks data before forwarding, corrects damaged groups, and adjusts the time sequence, but does not differentiate the priority.

If the signal is weak but still readable, the active hub restores it to a strong state before forwarding. This makes some devices with poor performance can be used normally. If the signal sent by a device is not strong enough to make the passive hub unidentifiable, the signal amplifier of the active hub can make the device continue to work normally. In addition, the active hub can also report device failures, providing a certain degree of diagnostic capability.

The active hub provides Optimized Performance and some diagnostic capabilities, and can be configured with multiple ports. Therefore, it is more expensive than a simple passive hub.

3. intelligent HUB)

Smart hubs provide more functions than the first two, allowing users to share resources more effectively. In addition to the features of the active hub, the smart hub provides a centralized management function. If an error occurs on the device connected to the smart hub, you can easily identify, diagnose, and fix it.

Another outstanding feature of smart hub is its ability to provide flexible transmission rates for different devices. In addition to the port connecting to the high-speed trunk, the smart Hub also supports a 10/16/Mbps rate to the desktop, that is, Ethernet, a licensing ring, and FDDI.

4. switching HUB)　

The switching set line set is a smart hub that provides the line switching capability and network segmentation capability in the general smart hub function. Since a hub is basically defined as a shared device, it is often included in the entry-level switch type.

The high-end Hub also provides other features, such as redundant AC power supply, built-in DC power supply, redundant fan, automatic disconnection of cable connections, hot swapping of modules, and polarity adjustment of 10Base-T connectors, for example, redundant storage and clock configurations, some hubs also integrate routing and bridging functions.

2. Select HUB　

Now the price of a 10 m non-smart HUB is very low, and the 10 m network does not require high transmission media and wiring, so many users who like DIY can do it on their own, build your own LAN or office LAN.

1. Based on selection of external dimensions

The purchase of a hub is generally after the Integrated Wiring ends and the backbone device is finalized. If your system is relatively simple and there are few users in the LAN, the SOHO series HUB will be more suitable for you. They generally have eight 10BaseTX ports. BNC and AUI ports are reserved for some hubs to take advantage of previously laid media such as coarse and fine cables. If you want to place network devices in a cabinet, you need to purchase a hub with a geometric size that complies with the rack standard. They comply with the 19 inch industrial specifications and can be easily installed in cabinets. Currently, these hubs use 12-port and 24-port devices as the mainstream. Some vendors still follow ~ The 16-port specification has the same industrial standards, so there will be no compatibility issues. You can select a hub with different port numbers based on the number of your sites.

2. Select bandwidth based　

The selection of hub bandwidth mainly depends on three factors.

(1) The bandwidth of the connected device. If the connected device is allowed to run 100 M, you can purchase M hub; otherwise, 10 M hub should be your ideal choice.

(2) Number of sites. Because all workstations connected to the Hub compete for the same upstream bus and are in the same conflicting domain, too many sites will cause a broadcast storm. Based on experience, the number of sites in the 10 m conflict domain should not exceed 25, and the number of sites in the M conflict domain should not exceed 35, in this case, replace the hub with a vswitch.

(3) Application requirements. Generally, the transmitted content does not involve speech or images. If the transmission volume is relatively small, 10 MB bandwidth is enough. If the transmission volume is large and multimedia applications are involved, note that 100 M is recommended when the hub is not suitable for transmitting time-sensitive signals. Now, the manufacturer provides a new solution, dual-speed hub, which has built-in 10 M and 10/100 M internal buses. Two-speed hubs are divided into manual 10/100 M switching and automatic M switching. Switch to per HUB manually, and switch to per Port automatically. Because of the two built-in bus in the double-speed HUB, there are two solutions for intercommunication between them: one is to use an internal bridge to connect the two bus and translate 10 M and M data packets. Second, the HUB does not have a built-in bridge, and the connected data link layer equipment is required for intercommunication. The price of built-in bridges is slightly different.

3. Selection Based on manageability

Because the HUB was originally a low-end product and cannot be managed. With the development of technology, some hubs can provide SNMP support for simple management of hubs by adding network management modules. It should be noted that, although SNMP is supported by the same vendor, modules of different vendors cannot be mixed, and even modules of different products of the same vendor are different.

4. Select an Extension Method

If you think the port is not enough, you can increase the number of ports in two ways.

(1) stackable hubs are generally expensive. As mentioned earlier, the number of sites in a conflicting domain should not be too large, and the number of stacked layers should not be too large. However, the more layers that can be stacked, the higher the stability of the HUB.

(2) There are two cascade methods for the current cascade HUB: If the HUB itself has a cascade port, the two hubs are connected in normal line order; If the cascade ports on the HUB, any two ports of the two hubs can be linked by a RJ-45 crossover.

There is also a built-in HUB, NICin HUB. It can be inserted in a PC or server, so you can have several more RJ-45 ports, other LAN users can directly inserted in these RJ-45 ports, very suitable for small office.

3. Use HUB

Through the above introduction, we know the characteristics of the HUB and how to purchase it. When our computer Nic and network cable are ready, how can we use the HUB to connect the network?

On the front panel of the HUB, there are multiple ports, namely the RJ-45 Jack, used to connect the network cable from computer and other network equipment, just need to plug the RJ-45 plug on the network cable into it, in these RJ-45 jacks, there is usually a special port called cascade ports used to connect to other hubs, cascade ports through the conversion switch next to the cascade function and common connection Function Conversion, in some cases, a cascade port is designed separately. The status indicators of each port are displayed on the panel. With these indicators, we can know which ports are connected to network devices and which ports are transmitting data, the Panel also has the power-on and working indicator of the hub itself.

There is a power outlet on the back of the hub for power connection, a stacked hub, and two upper and lower stacked ports for stacking. A dedicated connection line is used to connect the stacked ports of the two hubs to the stacked ports.

Connect the network cable and turn on the HUB power. Your Network will start to work physically. Of course, the network software on the computer needs to be installed, after the protocol is configured, the network can be installed and used.

We know that when we expand the network but the HUB port is not enough, we must add a HUB to provide more ports, which requires the connection between the two hubs. Generally, we use cascade to expand the HUB port, connect one end of the network cable to the common port of one HUB, and the other end to the cascade port of another HUB. In this way, the number of ports that the HUB can provide can be expanded. This method has a relationship between the upper and lower levels, so it is called cascade. From its working mode, we can see that it not only expands the port, but also expands the network distance, because each level of HUB has the function of amplifying and forwarding signals, however, the HUB also has its disadvantages. When the computers connected to the HUB of the next level access the computers of the previous level, the computers of the next level can only share the network bandwidth of the cascade line, the signal needs to search for the target port in the upper and lower ports respectively. Each HUB is like an independent information forwarder, which transmits signals at the first level.

By connecting a special connection to the stack port on the HUB, you can connect multiple hubs to expand the number of ports. Through the coordination of stacking lines, these stacked hubs work like a large HUB with many ports, this connection method avoids the disadvantages of cascade, such as shared cascade lines and multi-level information retrieval. This method is more efficient and reflects the speed advantage for vswitches. However, this HUB Connection Method limits the physical distance between the network device and the network center, and there are many lines in the Network Center.

1. Differences between low-price switches and hubs