General classification of switches

Computer A network is a group of computers connected to each other by a communication channel. The channel ensures data exchange within the network, that is, data exchange between computers of a given group. The network can consist of two or three computers, or it can unite several thousand PCs. Physically, data exchange between computers can be carried out via a special cable, fiber optic cable or through twisted pair.

Network hardware and hardware-software help connect computers into a network and ensure their interaction. These tools can be divided into the following groups according to their main functional purpose:

Passive network hardware connecting connectors, cables, patch cords, patch panels, telecommunication sockets, etc.;

Active network equipment converters/adapters, modems, repeaters, bridges, switches, routers, etc.

Currently development computer networks occurs in the following areas:

Speed ​​increase;

Implementation of switching-based segmentation;

Connecting networks using routing.

Layer 2 switching

Considering the properties of the second layer of the ISO/OSI reference model and its classical definition, we can see that this level belongs to the main share of commuting properties.

The data link layer ensures reliable transit of data across a physical channel. In particular, it addresses issues of physical addressing (as opposed to network or logical addressing), network topology, line discipline (how final system use a network channel), fault notifications, orderly delivery of data blocks and information flow control.

In fact, the functionality defined by the OSI data link layer serves as the platform for some of today's most powerful technologies. Great importance Layer 2 functionality is underscored by the fact that hardware manufacturers continue to invest heavily in developing devices with such functionality, i.e. switches.

Layer 3 switching

Layer 3 switching? This is hardware routing. Traditional routers implement their functions using software-controlled processors, which we will call software routing. Traditional routers typically forward packets at a rate of about 500,000 packets per second. Layer 3 switches today operate at speeds of up to 50 million packets per second. It is also possible to further increase it, since each interface module, as in the second level switch, is equipped with its own ASIC-based packet forwarding processor. So increasing the number of modules leads to increasing routing performance. Usage high speed technology large customized integrated circuits(ASIC) is main characteristic which differentiates Layer 3 switches from traditional routers.

A switch is a device that operates at the second/third level of the ISO/OSI reference model and is designed to combine network segments operating on the same link/network layer protocol. The switch routes traffic through only the one port needed to reach its destination.

The figure (see Figure 1) shows the classification of switches according to management capabilities and in accordance with reference model ISO/OSI.

Figure 1 Switch classification

Let's take a closer look at the purpose and capabilities of each type of switch.

Unmanaged switch? This is a device designed to connect several computer network nodes within one or more network segments. It transmits data only directly to the recipient, with the exception of broadcast traffic to all network nodes. An unmanaged switch cannot perform any other functions.

Managed switches are more complex devices that allow you to perform a set of functions of the second and third levels of the ISO/OSI model. They can be managed via the Web interface, command line via the console port or remotely via SSH, as well as using the SNMP protocol.

Configurable switches provide users with the ability to configure specific settings using simple management utilities, a Web interface, a simplified command line interface, and SNMP.

Layer 2 switches analyze incoming frames, decide on their further transmission, and forward them to destinations based on the OSI link layer MAC addresses. The main advantage of Layer 2 switches is transparency to upper-layer protocols. Since the switch operates at the second level, it does not need to analyze the information upper levels OSI models.

Layer 3 switches perform switching and filtering based on the addresses of the link (layer 2) and network (layer 3) layers of the OSI model. Such switches dynamically decide whether to switch (layer 2) or route (layer 3) incoming traffic. Layer 3 switches perform switching within working group and routing between different subnets or virtual local area networks (VLANs).

An unmanaged switch is suitable for building home network or small office networks. Its difference from the others is the “boxed” version. That is, after the purchase, it is enough to set up a connection to the provider’s server and you can distribute the Internet.

When working with such a switch, it is worth considering that short-term delays are possible when using voice pagers (Skype, Vo-IP) and the impossibility of distributing the Internet channel width. That is, when you turn on the Torrent program on one of the computers on the network, it will consume almost the entire bandwidth of the channel, and the rest of the computers on the network will use the remaining bandwidth.

A managed switch is The best decision for building a network in offices and computer clubs. This type Sold as standard and with standard settings.

To configure such a switch you will have to work hard - a large number of settings can make your head spin, but when the right approach bring wonderful results. main feature- distribution of channel width and configuration of the throughput of each port. Let's take as an example an Internet channel of 50 Mbps/s, 5 computers on the network, an IP-TV set-top box and an ATC. We can do several options, but I will consider only one.

Next - only your imagination and out-of-the-box thinking. In total we have relatively big canal. Why relatively? You will learn this information further if you carefully delve into the essence. I forgot to clarify - I'm putting together a network for a small office. IP-TV is used for TV in the waiting room, computers - for working with e-mail, transferring documents, browsing websites, ATC - for connecting landline phones to the main line for receiving calls from Skype, QIP, cell phones etc.

A managed switch is a modification of a regular, unmanaged switch.

In addition to the ASIC chip, it contains a microprocessor capable of performing additional operations on frames, such as filtering, modification and prioritization, as well as other actions not related to frame forwarding. For example, provide a user interface.

In practical terms, the differences between managed and unmanaged switches lie, firstly, in the list of supported standards - if a regular, unmanaged switch supports only the Ethernet standard (IEEE 802.3) in its various varieties, then managed switches support a much wider list of standards: 802.1Q. 802.1X, 802.1AE, 802.3ad (802.1AX) and so on, which require configuration and management.

There is another type - SMART switches.

The appearance of smart switches was due to a marketing move - the devices support a significantly smaller number of functions than their older brothers, but are nevertheless manageable.

In order not to confuse or mislead consumers, the first models were produced with the designation intelligent or web-managed.

These devices offered the basic functionality of managed switches at a significantly lower price - VLAN organization, administrative enabling and disabling of ports, filtering by MAC address or speed limiting. Traditionally, the only way management was a web interface, so the name web-managed was firmly assigned to smart switches.

The switch stores in associative memory a switching table that indicates the correspondence of the host MAC address to the switch port. When the switch is turned on, this table is empty, and it begins to operate in learning mode. In this mode, data arriving on any port is transmitted to all other ports of the switch. In this case, the switch analyzes the frames and, having determined the MAC address of the sending host, enters it into the table.

Subsequently, if one of the switch ports receives a frame intended for a host whose MAC address is already in the table, then this frame will be transmitted only through the port specified in the table. If the destination host's MAC address is not bound to any port on the switch, then the frame will be sent to all ports.

Over time, the switch builds full table for all its ports, and as a result the traffic is localized.

It is worth noting the low latency (delay) and high speed forwarding on each interface port.

Switching methods in a switch.

There are three switching methods. Each of them is a combination of parameters such as the waiting time for the switch to make a decision (latency) and transmission reliability.

With intermediate storage (Store and Forward).

“Cut-through”.

“Fragment-free” or hybrid.

With intermediate storage (Store and Forward). The switch reads all incoming information in the frame, checks it for errors, selects a switching port, and then sends the verified frame to it.

“Cut-through”. The switch reads only the destination address in the frame and then performs the switching. This mode reduces transmission delays, but does not have an error detection method.

“Fragment-free” or hybrid. This mode is a modification of the "All Around" mode. The transmission is carried out after filtering collision fragments (frames 64 bytes in size are processed using store-and-forward technology, the rest using cut-through technology). The "switch decision" delay is added to the time it takes a frame to enter and exit the switch port and determines total delay switch.

Switch performance characteristics.

The main characteristics of a switch that measure its performance are:

• - filtration speed;
• - routing speed (forwarding);
• - throughput;
• - frame transmission delay.

Additionally, there are several switch characteristics that have the greatest impact on these performance specifications. These include:

• - size of frame buffer(s);
• - internal bus performance;
• - performance of the processor or processors;
• - size of the internal address table.

Frame filtering and forwarding speed are two key performance characteristics of a switch. These characteristics are integral indicators; they do not depend on how the switch is technically implemented.

The filtering rate determines the speed at which the switch performs the following frame processing steps:

• - receiving the frame into your buffer;
• - destruction of the frame, since its destination port coincides with the source port.

The forwarding rate determines the speed at which the switch performs the following frame processing steps:

• - receiving the frame into your buffer;
• - viewing the address table to find the port for the frame's destination address;
• - transmission of the frame to the network through the destination port found in the address table.

Both filtering speed and forwarding speed are usually measured in frames per second.

If the characteristics of the switch do not specify for which protocol and for what frame size the filtering and forwarding speeds are given, then by default it is assumed that these indicators are given for the Ethernet protocol and frames 64 bytes long (without preamble), with a data field of 46 bytes .

The use of frames of minimum length as the main indicator of the speed of a switch is explained by the fact that such frames always create the most difficult operating mode for the switch compared to frames of other formats with equal throughput of transferred user data.

Therefore, when testing a switch, the minimum frame length mode is used as the most difficult test, which should verify the ability of the switch to operate under the worst combination of traffic parameters for it.

In addition, for packets of minimal length, the filtering and forwarding speeds are maximum value, which is of no small importance when advertising a switch.

The throughput of a switch is measured by the amount of user data transmitted per unit of time through its ports.

Since the switch operates at the data link level, its user data is the data that is transferred to the data field of data link layer protocol frames - Ethernet, Token Ring, FDDI, etc.

The maximum value of the switch throughput is always achieved on frames maximum length, since in this case the share of overhead costs for frame service information is much lower than for frames of minimum length, and the time the switch performs frame processing operations per byte of user information is significantly less.

The dependence of the switch's throughput on the size of transmitted frames is well illustrated by the example of the Ethernet protocol, for which, when transmitting frames of minimum length, a transmission speed of 14880 frames per second and a throughput of 5.48 Mb/s is achieved, and when transmitting frames of maximum length, a transmission speed of 812 frames per second is achieved. second and throughput 9.74 Mb/s.

Throughput drops almost twice when switching to frames of minimum length, and this does not take into account the loss of time for processing frames by the switch.

Frame transmission latency is measured as the time elapsed from the moment the first byte of the frame arrives at the input port of the switch until the moment this byte appears at the output port of the switch.

Latency consists of the time spent buffering the frame's bytes, as well as the time spent processing the frame by the switch - looking through the address table, making filtering or forwarding decisions, and gaining access to the egress port environment. The amount of delay introduced by the switch depends on its operating mode. If switching is carried out "on the fly", then the delays are usually small and range from 10 µs to 40 µs, and with full frame buffering - from 50 µs to 200 µs (for frames of minimum length). A switch is a multiport device, so it is customary to give all the above characteristics (except for frame transmission delay) in two versions:

• - the first option is the total performance of the switch with simultaneous transmission of traffic on all its ports;
• - the second option is the performance given per port.

Since when traffic is simultaneously transmitted by several ports, there is a huge number of traffic options, differing in the size of frames in the flow, the distribution of the average intensity of frame flows between destination ports, the coefficients of variation in the intensity of frame flows, etc., etc.

Then, when comparing switches by performance, it is necessary to take into account for which traffic variant the published performance data is obtained. Some laboratories that routinely test communications equipment have developed detailed descriptions conditions for testing switches and use them in their practice, however, these tests have not yet become common in industry. Ideally, a switch installed on a network transmits frames between nodes connected to its ports at the rate at which the nodes generate these frames, without introducing additional delays or losing a single frame.

In real practice, the switch always introduces some delays when transmitting frames, and may also lose some frames, that is, not deliver them to the recipients. Due to differences in internal organization different models switches, it is difficult to predict how a particular switch will transmit frames for any particular traffic pattern. The best criterion The practice still remains when the switch is placed in real network and the delays it introduces and the number of lost frames are measured. The overall performance of the switch is ensured by the sufficiently high performance of each of its individual elements - the port processor, switching matrix, common bus connecting modules, etc.

Regardless of the internal organization of the switch and the methods of pipelining its operations, it is possible to determine sufficiently simple requirements to the performance of its elements that are necessary to support a given traffic matrix. Because switch manufacturers strive to make their devices as fast as possible, the overall internal performance of a switch often exceeds by some margin the average amount of traffic that can be sent to the switch ports according to their protocols.

This type of switch is called non-blocking, i.e., any type of traffic is transmitted without reducing its intensity. In addition to the throughput of individual elements of the switch, such as port processors or the common bus, the performance of the switch is affected by such parameters as the size of the address table and the volume of the general buffer or individual port buffers.

The address table size affects the maximum capacity of the address table and determines maximum amount MAC addresses that the switch can simultaneously operate with.

Since switches most often use a dedicated processing unit to perform operations on each port with its own memory to store an instance of the address table, the size of the address table for switches is usually given per port.

Instances of the address table of different processor modules do not necessarily contain the same address information - most likely there will not be many duplicate addresses, unless the distribution of traffic on each port is completely equal among the other ports. Each port stores only those sets of addresses that it uses in Lately. The maximum number of MAC addresses that the port processor can remember depends on the application of the switch. Workgroup switches typically support only a few addresses per port because they are designed to form microsegments. Department switches must support several hundred addresses, and network backbone switches must support up to several thousand, typically 4000 - 8000 addresses. Insufficient address table capacity can cause the switch to slow down and the network to become clogged with excess traffic. If the port processor's address table is completely full, and it encounters a new source address in an incoming packet, then it must evict some old address and place a new one in its place. This operation itself will take some of the processor's time, but the main performance loss will be observed when a frame arrives with a destination address that had to be removed from the address table.

Since the frame's destination address is unknown, the switch must forward the frame to all other ports. This operation will create unnecessary work for many port processors, in addition, copies of this frame will end up on those network segments where they are completely unnecessary. Some switch manufacturers solve this problem by changing the algorithm for handling frames with an unknown destination address. One of the switch ports is configured as a trunk port, to which all frames with an unknown address are sent by default.

The switch's internal buffer memory is needed to temporarily store data frames in cases where they cannot be immediately transmitted to the output port. The buffer is designed to smooth out short-term traffic bursts.

After all, even if the traffic is well balanced and the performance of the port processors, as well as other processing elements of the switch, is sufficient to transmit average traffic values, this does not guarantee that their performance will be sufficient for very large peak loads. For example, traffic can arrive simultaneously at all switch inputs within a few tens of milliseconds, preventing it from transmitting received frames to output ports. To prevent frame loss when the average traffic intensity is repeatedly exceeded for a short time (and for local networks, traffic ripple coefficient values ​​in the range of 50-100 are often found), the only means is a large-volume buffer. As with address tables, each port processor module typically has its own buffer memory for storing frames. The larger the volume of this memory, the less likely it is that frames will be lost due to overloads, although if the average traffic values ​​are unbalanced, the buffer will sooner or later overflow.

Typically, switches designed to operate in critical parts of the network have a buffer memory of several tens or hundreds of kilobytes per port.

It is good when this buffer memory can be redistributed between several ports, since simultaneous overloads on several ports are unlikely. Additional means protection can be provided by a buffer common to all ports in the switch management module. Such a buffer usually has a capacity of several megabytes.

Ensuring the security of a computer network built on D-Link switches

graduate work

1.1.1 General classification of switches

A computer network is a group of computers connected to each other by a communication channel. The channel ensures data exchange within the network, that is, data exchange between computers of a given group. The network can consist of two or three computers, or it can unite several thousand PCs. Physically, data exchange between computers can be carried out over a special cable, fiber optic cable, or twisted pair cable.

Network hardware and hardware-software help connect computers into a network and ensure their interaction. These tools can be divided into the following groups according to their main functional purpose:

Passive network equipment connecting connectors, cables, patch cords, patch panels, telecommunication sockets, etc.;

Active network equipment converters/adapters, modems, repeaters, bridges, switches, routers, etc.

Currently, the development of computer networks occurs in the following areas:

Speed ​​increase;

Implementation of switching-based segmentation;

Connecting networks using routing.

Layer 2 switching

Considering the properties of the second level of the ISO/OSI reference model and its classical definition, you can see that this level owns the bulk of the switching properties.

The data link layer ensures reliable transit of data across a physical channel. In particular, it addresses issues of physical addressing (as opposed to network or logical addressing), network topology, line discipline (how the end system should use the network link), fault notification, ordering of data blocks, and information flow control.

In fact, the functionality defined by the OSI data link layer serves as the platform for some of today's most powerful technologies. The importance of Layer 2 functionality is underscored by the fact that hardware manufacturers continue to invest heavily in developing devices with such functionality, i.e. switches.

Layer 3 switching

Layer 3 switching? This is hardware routing. Traditional routers implement their functions using software-controlled processors, which we will call software routing. Traditional routers typically forward packets at a rate of about 500,000 packets per second. Layer 3 switches today operate at speeds of up to 50 million packets per second. It is also possible to further increase it, since each interface module, as in the second level switch, is equipped with its own ASIC-based packet forwarding processor. So increasing the number of modules leads to increasing routing performance. The use of high-speed large-scale integrated circuit (ASIC) technology is the main characteristic that distinguishes Layer 3 switches from traditional routers.

A switch is a device that operates at the second/third level of the ISO/OSI reference model and is designed to combine network segments operating on the same link/network layer protocol. The switch routes traffic through only the one port needed to reach its destination.

The figure (see Figure 1) shows the classification of switches by management capabilities and in accordance with the ISO/OSI reference model.

Posted on http://www.allbest.ru/

Figure 1 Switch classification

Let's take a closer look at the purpose and capabilities of each type of switch.

Unmanaged switch? This is a device designed to connect several computer network nodes within one or more network segments. It transmits data only directly to the recipient, with the exception of broadcast traffic to all network nodes. An unmanaged switch cannot perform any other functions.

Managed switches are more complex devices that allow you to perform a set of functions of the second and third levels of the ISO/OSI model. They can be managed via the Web interface, command line via the console port or remotely via SSH, as well as using the SNMP protocol.

Configurable switches provide users with the ability to configure specific settings using simple management utilities, a Web interface, a simplified command line interface, and SNMP.

Layer 2 switches analyze incoming frames, decide on their further transmission, and forward them to destinations based on the OSI link layer MAC addresses. The main advantage of Layer 2 switches is transparency to upper-layer protocols. Since the switch operates at layer 2, it does not need to analyze information from the upper layers of the OSI model.

Layer 3 switches perform switching and filtering based on the addresses of the link (layer 2) and network (layer 3) layers of the OSI model. Such switches dynamically decide whether to switch (layer 2) or route (layer 3) incoming traffic. Layer 3 switches perform switching within a workgroup and routing between different subnets or virtual local area networks (VLANs).

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if possible, control. There are three categories of switches:

• unmanaged switches;
• managed switches;
• custom switches.

Unmanaged switches do not support management and update capabilities software.

Managed Switches are complex devices that allow you to perform an expanded set of functions of the 2nd and 3rd layers of the OSI model. Switches can be managed via a Web interface, command line (CLI), SNMP, Telnet, etc.

Custom Switches occupy an intermediate position between them. They provide users with the ability to configure certain network parameters using intuitive management utilities, a Web interface, a simplified command line interface, and the SNMP protocol.

Switch Management Tools

Most modern switches support various functions management and monitoring. These include a user-friendly Web management interface, Command Line Interface (CLI), Telnet, SNMP management. In D-Link switches Smart series support has also been implemented initial setup and software updates through the D-Link SmartConsole Utility.

The Web-based management interface allows you to configure and monitor switch parameters using any computer equipped with a standard Web browser. The browser is a universal access tool and can directly connect to the switch via HTTP.

Home page Web interface provides access to various settings switch and displays all necessary information about the device. The administrator can quickly view the device status, performance statistics, etc., and make the necessary settings.

The switch's command line interface is accessed by connecting a terminal or personal computer to its console port. installed program terminal emulation. This access method is most convenient when connecting to the switch for the first time, when the IP address value is unknown or not set, when you need to recover a password, and when performing advanced switch settings. The command line interface can also be accessed over the network using the Telnet protocol.

The user can use any management interface convenient for him to configure the switch, because set available via different interfaces control functions are the same for each specific model.

Another way to manage the switch is to use the SNMP (Simple Network Management Protocol). The SNMP protocol is a Layer 7 protocol of the OSI model and is designed specifically for managing and monitoring network devices and communication applications. This is done by exchanging control information between agents located on network devices, and managers located at control stations. D-Link switches support SNMP versions 1, 2c and 3.

It is also worth noting the ability to update the software of switches (with the exception of unmanaged ones). This ensures a longer service life of the devices, because allows you to add new functions or eliminate existing errors as new software versions are released, which significantly facilitates and reduces the cost of using devices. D-Link Company distributes new versions of software free of charge. This can also include the ability to save switch settings in case of failures with subsequent restoration or replication, which saves the administrator from performing routine work.

Connecting to a switch

Before you begin configuring the switch, you must install physical connection between him and workstation. There are two types cable connection, used to manage the switch. The first type is through the console port (if the device has one), the second is through the Ethernet port (via the Telnet protocol or via the Web interface). The console port is used for initial configuration of the switch and typically does not require configuration. In order to access the switch via the Ethernet port, you must enter the default IP address of its management interface in your browser (usually this is listed in the user manual).

When connecting to the copper (RJ-45) Ethernet switch port of Ethernet-compatible servers, routers, or workstations, use a four-pair Category 5, 5e, or 6 UTP cable for Gigabit Ethernet. Since D-Link switches support automatic polarity detection (MDI/MDIX), you can use any type of cable (straight-through or crossover).

Rice. 2.1.

To connect to a copper (RJ-45 connector) Ethernet port of another switch, you can also use any four-pair UTP category 5, 5e, 6 cable, provided that the switch ports support automatic polarity detection. Otherwise, you must use a crossover cable.

Rice. 2.2.

The LED indicator of the port will help determine whether the connection is correct. If the corresponding LED is lit, communication between the switch and the connected device is established. If the indicator is not lit, one of the devices may not be powered on, or there may be a problem with the network adapter connected device, or there is a problem with the cable. If the light comes on and goes off, there may be a problem with automatic detection speed and operating mode (duplex/half-duplex) (for detailed description indicators, refer to the user manual for your specific switch model).

Connecting to the Switch CLI Console

D-Link managed switches are equipped with a console port. Depending on the switch model, the console port may have a DB-9 or RJ-45 connector. Using the console cable included in the package, the switch is connected to the serial port of the computer. A console connection is sometimes called an "Out-of-Band connection." This means that the console uses a different network connection circuit (does not use the bandwidth of the Ethernet ports).

After connecting to the console port of the switch on personal computer You must run a VT100 terminal emulation program (for example, the HyperTerminal program in Windows). The program should be installed following parameters connections, which are usually indicated in the documentation for the device:

All managed switches are protected against access by unauthorized users, so you will be prompted to enter your username and password after the device boots up. By default, the username and password are not defined, so you need to double-click Enter key. After that in command line The following prompt appears, for example DES-3528# . Now you can enter commands.

Rice. 2.3.

Designed for use with a small number of users, desktop switches can serve as replacements for 10Base-T hubs. Typically, desktop switches have 24 ports, each of which supports a personal (private) channel with a bandwidth of 10 Mbit/s for connecting one node (for example, a workstation). Additionally, such a switch may have one or more 100Base-T or FDDI ports for connecting to a backbone or server.

By combining the capabilities of 10 Mbps and 100 Mbps technologies, desktop switches minimize blocking when trying to simultaneous connection several nodes to a single high-speed port (100 Mbit/s). In a client-server environment, multiple nodes can simultaneously access a server connected through a 100 Mbps port.

Desktop switches are easy to install and maintain, often include built-in plug-and-play software and have a simplified configuration interface. The cost per port is $150, less than twice the cost per port in 10Base-T hubs.

Backbone switches

At the top of the hierarchy Ethernet switches There are backbone switches - devices for connecting networks or segments that support multi-homing for their ports. Such switches are used to connect 10Base-T hubs, desktop and group switches, and servers.

For users who want to increase their available bandwidth through segmentation, core switches provide a simple, high-performance, and cost-effective alternative to routers. Backbone switches can simultaneously forward traffic between multiple segments with full use bandwidth of the medium.

In addition, backbone switches can filter packets based on attributes other than addresses. For example, an administrator can prevent NetWare broadcast packets from being transmitted to Unix workstations through protocol filtering.

Backbone switches are characterized by a modular design and the ability to support up to several thousand MAC addresses per port. These switches are more complex to install than desktop switches, mainly due to the need to configure routing functionality. Backup sources power supply, hot-swappable modules, support for the Spanning Tree protocol are mandatory elements for backbone switches, providing all the capabilities of switching technologies, including virtual networks.

At sharing with desktop switches (instead of 10Base-T hubs), backbone switches provide end-to-end switching, which avoids most of the problems associated with using a shared environment (a large number of collisions, propagation of erroneous packets, reduced security). In the majority powerful applications 100 Mbps backbone switches can serve as a high-speed backbone between 100/10 Mbps desktop switches and servers connected via a 100 Mbps link.

The cost of backbone switches per port is $750 - $1500.

Workgroup Switches

Workgroup switches are used primarily to connect isolated desktop switches or 10Base-T hubs to the rest of the network. These devices combine the properties of both desktop and backbone switches.

Like backbone workgroup switches, they can support multihoming (up to several thousand MAC addresses per switch) and can be used as routers. Like desktop switches, they can be used to connect to the ports of individual nodes.

Although workgroup switches typically do not support protocol filtering and other routing features, some switches of this type support Spanning Tree, SNMP, and virtual networking.

The 10 Mbps connection between the switch and the user node (workstation) is most often done using unshielded twisted pair (UTP) cable, while the high-speed port uses twisted pair or optical cable. Multicast switches can support several thousand MAC addresses per device, with ports used to connect a small number of hubs or trunks. Group switches should then support Spanning Tree to simplify the network configuration and allow channel duplication without creating loops in the network.

A key application for workgroup switches is to replace 10Base-T hubs and routers, allowing users to move from shared to private by simultaneously supporting shared and personal 10 Mbps connections. Some group switches have fault-tolerant functions, but group switches never support protocol filtering.

The cost per port for workgroup switches is $250 - $1000.