03/18/1997 Dmitry Ganzha

Switches occupy a central place in modern local area networks. TYPES OF SWITCHING SWITCHING HUBS METHODS OF PACKET PROCESSING RISC AND ASIC ARCHITECTURE OF HIGH-CLASS SWITCHES BUILDING VIRTUAL NETWORKS THIRD LEVEL SWITCHING CONCLUSION Switching is one of the most popular modern technologies.

Switches occupy a central place in modern local area networks.

Switching is one of the most popular modern technologies. Switches are displacing bridges and routers to the periphery of local networks, leaving behind them the role of organizing communications through the global network. This popularity of switches is primarily due to the fact that they allow, through microsegmentation, to increase network performance compared to shared networks with the same nominal bandwidth. In addition to dividing the network into small segments, switches make it possible to organize connected devices into logical networks and easily regroup them when necessary; in other words, they allow you to create virtual networks.

What is a switch? According to the IDC definition, "a switch is a device designed like a hub and acting as a high-speed multiport bridge; the built-in switching mechanism allows for segmentation local network and allocate bandwidth to end stations in the network" (see article by M. Kulgin "Build a network, plant a tree..." in the February issue LAN). However, this definition applies primarily to frame switches.

TYPES OF SWITCHING

Switching usually refers to four different technologies - configuration switching, frame switching, cell switching, and frame-to-cell conversion.

Configuration switching is also known as port switching, where a specific port on a smart hub module is assigned to one of the internal Ethernet segments (or Token Ring). This assignment is made remotely through software network management when users and resources join or move on the network. Unlike other switching technologies, this method does not improve the performance of the shared LAN.

Frame switching, or LAN switching, uses standard Ethernet (or Token Ring) frame formats. Each frame is processed by the nearest switch and transmitted further across the network directly to the recipient. As a result, the network turns into a set of parallel high-speed direct channels. We will look at how frame switching is carried out inside a switch below using the example of a switching hub.

Cell switching is used in ATM. The use of small fixed-length cells makes it possible to create low-cost, high-speed switching structures at the hardware level. Both frame switches and mesh switches can support multiple independent workgroups regardless of their physical connection (see the section "Building virtual networks").

The conversion between frames and cells allows, for example, a station with an Ethernet card to communicate directly with devices on an ATM network. This technology is used to emulate a local network.

In this lesson we will be primarily interested in frame switching.

SWITCHING HUBS

The first switching hub, called EtherSwictch, was introduced by Kalpana. This hub made it possible to reduce network contention by reducing the number of nodes in a logical segment using microsegmentation technology. Essentially, the number of stations in one segment was reduced to two: the station initiating the request and the station responding to the request. No other station sees the information transmitted between them. Packets are transmitted as if through a bridge, but without the delay inherent in a bridge.

In a switched Ethernet network, each member of a group of multiple users can be simultaneously guaranteed 10 Mbps throughput. The best way to understand how such a hub works is to use an analogy with a regular old telephone switch, in which the participants in the dialogue are connected by a coaxial cable. When a subscriber called “eternal” 07 and asked to be connected to such and such a number, the operator first of all checked whether the line was available; if so, he connected the participants directly using a piece of cable. No one else (with the exception of the intelligence services, of course) could hear their conversation. After the call ended, the operator disconnected the cable from both ports and waited for the next call.

Switching hubs operate in a similar way (see Figure 1): they forward packets from an input port to an output port through the switch fabric. When a packet arrives at an input port, the switch reads its MAC address (i.e., layer 2 address) and it is immediately forwarded to the port associated with that address. If the port is busy, the packet is placed in a queue. Essentially, a queue is a buffer at the input port where packets wait until desired port will be released. However, the buffering methods are slightly different.

Picture 1.
Switching hubs function similarly to older telephone switches: they connect an input port directly to an output port through a switch fabric.

PACKET PROCESSING METHODS

In end-to-end switching (also called in-flight switching and bufferless switching), the switch reads only the address of the incoming packet. The packet is transmitted further regardless of the absence or presence of errors in it. This can significantly reduce packet processing time, since only the first few bytes are read. Therefore, it is up to the receiving party to identify defective packets and request their retransmission. However, modern cable systems are reliable enough that the need for retransmission on many networks is minimal. However, no one is immune to errors in the event of a damaged cable, faulty network card, or interference from an external electromagnetic source.

When switching with intermediate buffering, the switch, receiving a packet, does not transmit it further until it reads it completely, or at least reads all the information it needs. It not only determines the recipient's address, but also checks the checksum, i.e. it can cut off defective packets. This allows you to isolate the error-producing segment. Thus, buffer-and-forward switching emphasizes reliability rather than speed.

Apart from the above two, some switches use a hybrid method. Under normal conditions, they provide end-to-end switching, but monitor the number of errors by checking checksums. If the number of errors reaches a specified threshold, they enter switching mode with forward buffering. When the number of errors decreases to an acceptable level, they return to end-to-end switching mode. This type of switching is called threshold or adaptive switching.

RISC AND ASIC

Often, buffer-forward switches are implemented using standard RISC processors. One advantage of this approach is that it is relatively inexpensive compared to ASIC switches, but it is not very good for specialized applications. Switching in such devices is carried out using software, therefore their functionality can be changed by upgrading the installed software. Their disadvantage is that they are slower than ASIC-based switches.

Switches with ASIC integrated circuits are designed to perform specialized tasks: all their functionality is “hardwired” into the hardware. There is also a drawback to this approach: when modernization is necessary, the manufacturer is forced to rework the circuit. ASICs typically provide end-to-end switching. The switch fabric ASIC creates dedicated physical paths between an input and output port, as shown in .

ARCHITECTURE OF HIGH-CLASS SWITCHES

High-end switches are typically modular in design and can perform both packet and cell switching. The modules of such a switch perform switching between networks of different types, including Ethernet, Fast Ethernet, Token Ring, FDDI and ATM. In this case, the main switching mechanism in such devices is the ATM switching structure. We will look at the architecture of such devices using the Bay Networks Centillion 100 as an example.

Switching is accomplished using the following three hardware components (see Figure 2):

ATM backplane for ultra-high-speed cell transfer between modules;

a CellManager special-purpose integrated circuit on each module to control cell transfer across the backplane;

a special-purpose SAR integrated circuit on each module to convert frames to cells and vice versa.

(1x1)

Figure 2.
Cell switching is increasingly being used in high-end switches due to its high speed and ease of migration to ATM.

Each switch module has I/O ports, buffer memory, and a CellManager ASIC. In addition, each LAN module also has a RISC processor to perform frame switching between local ports and a packet assembler/disassembler to convert frames and cells into each other. All modules can independently switch between their ports, so that only traffic destined for other modules is sent through the backplane.

Each module maintains its own table of addresses, and the main control processor combines them into one common table, so that an individual module can see the network as a whole. If, for example, an Ethernet module receives a packet, it determines who the packet is addressed to. If the address is in the local address table, then the RISC processor switches the packet between local ports. If the destination is on another module, then the assembler/disassembler converts the packet into cells. The CellManager specifies a destination mask to identify the module(s) and port(s) to which the cells payload is destined. Any module whose board mask bit is specified in the destination mask copies the cell to local memory and transmits the data to the corresponding output port in accordance with the specified port mask bits.

BUILDING VIRTUAL NETWORKS

In addition to increasing productivity, switches allow you to create virtual networks. One of the methods for creating a virtual network is to create a broadcast domain through a logical connection of ports within the physical infrastructure of a communication device (this can be either a smart hub - configuration switching or a switch - frame switching). For example, the odd ports of an eight-port device are assigned to one virtual network, and the even ports are assigned to another. As a result, a station in one virtual network becomes isolated from stations in another. The disadvantage of this method of organizing a virtual network is that all stations connected to the same port must belong to the same virtual network.

Another method for creating a virtual network is based on the MAC addresses of connected devices. With this method of organizing a virtual network, any employee can connect, for example, his laptop computer to any switch port, and it will automatically determine whether his user belongs to a particular virtual network based on the MAC address. This method also allows users connected to the same switch port to belong to different virtual networks. Read more about virtual networks see the article by A. Avduevsky “Such real virtual networks” in the March issue of LAN for this year.

LEVEL 3 SWITCHING

For all their advantages, switches have one significant drawback: they are unable to protect the network from avalanches of broadcast packets, and this leads to unproductive network load and increased response time. Routers can monitor and filter unnecessary broadcast traffic, but they are orders of magnitude slower. Thus, according to Case Technologies documentation, the typical performance of a router is 10,000 packets per second, and this cannot be compared with the same indicator of a switch - 600,000 packets per second.

As a result, many manufacturers have begun to build routing capabilities into switches. To prevent the switch from slowing down significantly, various methods are used: for example, both Layer 2 switching and Layer 3 switching are implemented directly in hardware(in ASIC integrated circuits). Different manufacturers call this technology differently, but the goal is the same: the routing switch must perform Layer 3 functions at the same speed as Layer 2 functions. An important factor is the price of such a device per port: it should also be low, like that of switches (see article by Nick Lippis in the next issue of LAN magazine).

CONCLUSION

Switches are both structurally and functionally very diverse; It is impossible to cover all their aspects in one short article. In the next tutorial, we'll take a closer look at ATM switches.

Dmitry Ganzha is the executive editor of LAN. He can be contacted at: [email protected].

Switches in the local network

Switch one of critical devices used in building a local network. In this article we will talk about what switches are and focus on the important characteristics that need to be taken into account when choosing a local network switch.

First, let's look at the general block diagram to understand what place the switch occupies in the enterprise local network.

The picture above shows the most common structural scheme small local network. As a rule, access switches are used in such local networks.

Access switches are directly connected to end users, providing them with access to local network resources.

However, in large local networks, switches perform the following functions:

Network access level. As mentioned above, access switches provide connection points for end-user devices. In large local networks, access switch frames do not communicate with each other, but are transmitted through distribution switches.

Distribution level. Switches at this layer forward traffic between access switches, but do not interact with end users.

System kernel level. Devices of this type combine data transmission channels from distribution level switches in large territorial local networks and provide very high speed switching of data flows.

Switches are:

Unmanaged switches. These are ordinary stand-alone devices on a local network that manage data transfer independently and do not have the possibility of additional configuration. Due to ease of installation and low price, they are widely used for installation at home and in small businesses.

Managed Switches. More advanced and expensive devices. They allow the network administrator to independently configure them for specified tasks.

Managed switches can be configured in one of the following ways:

Via console port Via WEB interface

Through Telnet Via SNMP protocol

Via SSH

Switch levels

All switches can be divided into model levels OSI . The higher this level, the greater the capabilities the switch has, however, its cost will be significantly higher.

Layer 1 switches. This level includes hubs, repeaters and other devices operating at the physical level. These devices were present at the dawn of the development of the Internet and are currently not used on the local network. Having received a signal, a device of this type simply transmits it further to all ports except the sender port

Layer 2 switches2) . This level includes unmanaged and some managed switches ( switch ) working at the link level of the model OSI . Second-level switches work with frames - frames: a stream of data divided into portions. Having received the frame, the layer 2 switch reads the sender's address from the frame and enters it into its table MAC addresses, matching this address to the port on which it received this frame. Thanks to this approach, Layer 2 switches forward data only to the destination port, without creating excess traffic on other ports. Layer 2 switches don't understand IP addresses located on the third network level models OSI and work only at the link level.

Layer 2 switches support the most common protocols such as:

IEEE 802.1 q or VLAN virtual local networks. This protocol allows you to create separate logical networks within the same physical network.

For example, devices connected to the same switch, but located in different VLAN will not see each other and will be able to transmit data only in their own broadcast domain (devices from the same VLAN). Between themselves, the computers in the figure above will be able to transfer data using a device operating at the third level with IP addresses: router.

IEEE 802.1p (Priority tags ). This protocol is natively present in the protocol IEEE 802.1q and is a 3-bit field from 0 to 7. This protocol allows you to mark and sort all traffic by importance by setting priorities (maximum priority 7). Frames with higher priority will be forwarded first.

IEEE 802.1d Spanning tree protocol (STP).This protocol builds a local network in the form of a tree structure to avoid network loops and prevent the formation of a network storm.

Let's say the local network is installed in the form of a ring to increase the fault tolerance of the system. The switch with the highest priority in the network is selected as the root switch.In the example above, SW3 is the root. Without delving into protocol execution algorithms, switches calculate the path with the maximum cost and block it. For example, in our case, the shortest path from SW3 to SW1 and SW2 will be through its own dedicated interfaces (DP) Fa 0/1 and Fa 0/2. In this case, the default path price for the 100 Mbit/s interface will be 19. Interface Fa 0/1 of the local network switch SW1 is blocked because the total path price will be the sum of two transitions between 100 Mbit/s interfaces 19+19=38.

If the working route is damaged, the switches will recalculate the path and unblock this port

IEEE 802.1w Rapid spanning tree protocol (RSTP).Enhanced 802.1 standard d , which has higher stability and shorter recovery time of the communication line.

IEEE 802.1s Multiple spanning tree protocol.The latest version, taking into account all the shortcomings of the protocols STP and RSTP.

IEEE 802.3ad Link aggregation for parallel link.This protocol allows you to combine ports into groups. Total speed of this port aggregation will be the sum of the speeds of each port in it.The maximum speed is determined by the IEEE 802.3ad standard and is 8 Gbit/s.

Layer 3 switches3) . These devices are also called multiswitches since they combine the capabilities of switches operating at the second level and routers operating with IP packages at the third level.Layer 3 switches fully support all the features and standards of Layer 2 switches. Network devices can be accessed using IP addresses. A layer 3 switch supports the establishment of various connections: l 2 tp, pptp, pppoe, vpn, etc.

Layer 4 switches 4) . L4 level devices operating at the transport layer model OSI . Responsible for ensuring the reliability of data transmission. These switches can, based on information from the packet headers, understand the identity of the traffic different applications and make decisions about rerouting such traffic based on this information. The name of such devices is not settled; sometimes they are called smart switches, or L4 switches.

Main characteristics of switches

Number of ports. Currently, there are switches with the number of ports from 5 to 48. The number of network devices that can be connected to a given switch depends on this parameter.

For example, when building a small local network of 15 computers, we will need a switch with 16 ports: 15 for connecting end devices and one for installing and connecting a router to access the Internet.

Data transfer rate. This is the speed at which each switch port operates. Typically speeds are specified as follows: 10/100/1000 Mbit/s. The speed of the port is determined during auto negotiation with the end device. On managed switches, this parameter can be configured manually.

For example : A PC client device with a 1 Gbps network card is connected to a switch port with an operating speed of 10/100 Mbps c . As a result of auto-negotiation, devices agree to use the maximum possible speed of 100 Mbps.

Auto port negotiation between Full – duplex and half – duplex. Full – duplex: Data transfer is carried out simultaneously in two directions. Half-duplex Data transmission is carried out first in one direction, then in the other direction sequentially.

Internal fabric bandwidth. This parameter shows the overall speed at which the switch can process data from all ports.

For example: on a local network there is a switch with 5 ports operating at a speed of 10/100 Mbit/s. IN technical specifications switching matrix parameter is 1 Gbit/ c . This means that each port is in Full-duplex can operate at a speed of 200 Mbit/ c (100 Mbit/s reception and 100 Mbit/s transmission). Let's assume that the parameter of this switching matrix is ​​less than the specified one. This means that during peak loads, the ports will not be able to operate at the declared speed of 100 Mbit/s.

Auto MDI/MDI-X cable type negotiation. This function allows you to determine which of the two methods the EIA/TIA-568A or EIA/TIA-568B twisted pair was crimped. When installing local networks, the EIA/TIA-568B scheme is most widely used.

Stacking is the combination of several switches into one single logical device. Different switch manufacturers use their own stacking technologies, e.g. c isco uses Stack Wise stacking technology with a 32 Gbps bus between switches and Stack Wise Plus with a 64 Gbps bus between switches.

For example, this technology is relevant in large local networks, where it is necessary to connect more than 48 ports on the basis of one device.

Mounting for 19" rack. In home environments and small local networks, switches are often installed on flat surfaces or mounted on the wall, but the presence of so-called “ears” is necessary in larger local networks where active equipment is located in server cabinets.

MAC table sizeaddresses A switch is a device operating at level 2 of the model OSI . Unlike a hub, which simply redirects the received frame to all ports except the sender port, the switch learns: remembers MAC address of the sender's device, entering it, port number and lifetime of the entry into the table. Using this table, the switch does not forward the frame to all ports, but only to the recipient port. If the number of network devices in the local network is significant and the table size is full, the switch begins to overwrite older entries in the table and writes new ones, which significantly reduces the speed of the switch.

Jumboframe . This feature allows the switch to handle larger packet sizes than those defined by the Ethernet standard. After each packet is received, some time is spent processing it. When using an increased packet size using Jumbo Frame technology, you can save on packet processing time in networks that use data transfer rates of 1 Gb/sec and higher. At a lower speed there is no big gain

Switching modes.In order to understand the principle of operation of switching modes, first consider the structure of the frame transmitted to channel levels between a network device and a switch on a local network:

As can be seen from the picture:

• First comes the preamble signaling the start of frame transmission,
• Then MAC destination address ( DA) and MAC sender's address ( S.A.)
• Third level ID: IPv 4 or IPv 6 is used
payload)
• And at the end the checksum FCS: A 4 byte CRC value used to detect transmission errors. Calculated by the sending party, and placed in the FCS field. The receiving party calculates this value independently and compares it with the received value.

Now let's look at the switching modes:

Store - and - forward. This switching mode saves the entire frame to a buffer and checks the field FCS , which is at the very end of the frame and if the checksum of this field does not match, discards the entire frame. As a result, the likelihood of network congestion is reduced, since it is possible to discard frames with errors and delay the transmission time of the packet. This technology present in more expensive switches.

Cut-through. Simpler technology. In this case, frames can be processed faster, since they are not completely saved to the buffer. For analysis, data from the beginning of the frame to MAC address destination (DA) inclusive. The switch reads this MAC address and forwards it to the destination. The disadvantage of this technology is that the switch in this case forwards both dwarf packets with a length of less than 512 bit intervals and damaged packets, increasing the load on the local network.

PoE technology support

Pover over ethernet technology allows you to power a network device over the same cable. This decision allows you to reduce the cost of additional installation of supply lines.

The following PoE standards exist:

PoE 802.3af supports equipment up to 15.4 W

PoE 802.3at supports equipment up to 30W

Passive PoE

PoE 802.3 af/at have intelligent control circuits for supplying voltage to the device: before supplying power to the PoE device, the af/at standard source negotiates with it to avoid damage to the device. Passiv PoE is much cheaper than the first two standards; power is directly supplied to the device via free pairs of the network cable without any coordination.

Characteristics of standards

The PoE 802.3af standard is supported by most low-cost IP cameras, IP phones and access points.

The PoE 802.3at standard is present in more expensive models IP CCTV cameras where it is not possible to keep within 15.4 W. In this case, both the IP video camera and the PoE source (switch) must support this standard.

Expansion slots. Switches may have additional expansion slots. The most common are SFP modules (Small Form-factor Pluggable). Modular, compact transceivers used for data transmission in a telecommunications environment.

SFP modules are inserted into a free SFP port of a router, switch, multiplexer or media converter. Although SFP Ethernet modules exist, the most commonFiber optic modules are used to connect the main channel when transmitting data over long distances beyond the reach of the Ethernet standard. SFP modules are selected depending on distance and data transfer speed. The most common are dual-fiber SFP modules, which use one fiber for receiving and the other for transmitting data. However, WDM technology allows data transmission at different wavelengths over a single optical cable.

SFP modules are:

• SX - 850 nm used with multimode optical cable over distances up to 550m
• LX - 1310 nm is used with both types of optical cable (SM and MM) at a distance of up to 10 km
• BX - 1310/1550 nm is used with both types of optical cable (SM and MM) at a distance of up to 10 km
• XD - 1550 nm is used with single mode cable up to 40 km, ZX up to 80 km, EZ or EZX up to 120 km and DWDM

The SFP standard itself provides for data transmission at a speed of 1 Gbit/s, or at a speed of 100 Mbit/s. For faster data transfer, SFP+ modules were developed:

• SFP+ data transfer at 10 Gbps
• XFP data transfer at 10 Gbps
• QSFP+ data transfer at 40 Gbps
• CFP data transfer at 100 Gbps

However, at higher speeds, signals are processed at high frequencies. This requires greater heat dissipation and, accordingly, larger dimensions. Therefore, in fact, the SFP form factor is still preserved only in SFP+ modules.

Conclusion

Many readers have probably come across unmanaged switches and low-cost managed layer 2 switches in small local networks. However, the choice of switches for building larger and technically complex local networks is best left to professionals.

Safe Kuban uses switches of the following brands when installing local networks:

Professional Solution:

Cisco

Qtech

Budget solution

D-Link

Tp-Link

Tenda

Safe Kuban carries out installation, commissioning and maintenance of local networks in Krasnodar and the South of Russia.

Issues of building local networks seem very complex to non-specialist users due to the extensive terminological dictionary. Hubs and switches are imagined as complex equipment reminiscent of telephone exchanges, and the creation of a local home network becomes a reason to contact specialists. In fact, the switch is not as scary as its name: both devices are elementary network nodes that have minimal functionality, do not require knowledge of installation and operation, and are quite accessible to everyone.

Definition

Hub— a network hub designed to connect computers into a single local network by connecting Ethernet cables.

Switch(switch) is a network switch designed to connect several computers into a local network via an Ethernet interface.

Comparison

As we can see from the definition, the difference between a hub and a switch is related to the type of device: hub and switch. Despite one task - organizing a local network via Ethernet - devices approach its solution in different ways. A hub is a simple splitter that provides a direct connection between network clients. A switch is a more “smart” device that distributes data packets between clients in accordance with the request.

The hub, receiving a signal from one node, transmits it to all connected devices, and reception depends entirely on the recipient: the computer itself must recognize whether the packet is intended for it. Naturally, the answer assumes the same pattern. The signal pokes into all segments of the network until it finds one that will receive it. This circumstance reduces network throughput (and data exchange speed, respectively). The switch, receiving a data packet from the computer, sends it exactly to the address that was specified by the sender, relieving the network of load. A network organized through a switch is considered more secure: traffic exchange occurs directly between two clients, and others cannot process a signal that is not intended for them. Unlike a hub, a switch provides high throughput of the created network.

Logitec LAN-SW/PS Hub

Switch requires correct settings network card of the client computer: the IP address and subnet mask must match each other (the subnet mask indicates part of the IP address as the network address, and the other part as the client address). The hub does not require any settings, because it works at the physical level of the OSI network model, broadcasting a signal. The switch operates at the channel level, exchanging data packets. Another feature of the hub is the equalization of nodes in terms of data transfer speed, focusing on the lowest rates.

Switch COMPEX PS2208B

Conclusions website

1. Hub is a hub, switch is a switch.
2. The hub device is the simplest, the switch is more “intelligent”.
3. The hub transmits the signal to all network clients, the switch only to the recipient.
4. The performance of a network organized through a switch is higher.
5. The switch provides a higher level of data transmission security.
6. The hub operates at the physical layer of the OSI network model, the switch at the channel layer.
7. The switch requires proper configuration of network cards of network clients.

If previously the network cable through which data was transferred was simply connected directly to the computer, now the situation has changed. In one residential apartment, office or large company, there is often a need to create a computer network.

For this purpose, devices that are included in the “computer equipment” category are used. Such devices also include a switch that allows . So what is a switch, and how to use it to build a computer network?

What are switch devices used for?

Literally translated from in English, computer term“switch” refers to a device that is used to create a local network by connecting several computers. A synonym for the word switch is switch or switch.

A switch is a kind of bridge with many ports through which packet data is transmitted to specific recipients. The switch helps optimize the operation of the network, reduces the load on it, increases the level of security, and records individual MAC addresses, which allows you to quickly and efficiently transfer data.

Such switches were able to displace hubs, which were previously used to build computer networks. A switch is a smart device that can process received information about connected devices and then redirect the data to a specific address. As a result, network performance increases several times and Internet speeds up.

Types of equipment

Switch devices are divided into different types according to the following criteria:

• Type of ports.
• Number of ports.
• Port speeds are 10 Mbit/s, 100 Mbit/s and 1000 Sbit/s.
• Managed and unmanaged devices.
• Manufacturers.
• Functions.
• Specifications.

By the number of ports, switch switches are divided into:

• 8-port.
• 16-port.
• 24-port.
• 48-port.

For home and small office, a switch with 8 or 16 ports that operate at a speed of 100 Mbit/second is suitable.

For large enterprises, companies and firms, ports with an operating speed of 1000 Mbit per second are needed. Such devices are needed to connect servers and large communications equipment.

Unmanaged switches are the simplest of equipment. Complex switches are managed at the network or third layer of the OSI model - Layer 3 Switch.

Management is also carried out through methods such as:

• Web interface.
• Command line interface.
• SNMP and RMON protocols.

Complex or managed switches allow VLAN, QoS, mirroring, and aggregation features. Also, such switches are combined into one device called a stack. It is designed to increase the number of ports. Other ports are used for stacking.

What do providers use?




When creating a computer network, provider companies create one of its levels:

• Access level.
• Aggregation level.
• Kernel level.

Levels are needed to make it easier to handle the network: scale, configure, introduce redundancy, design the network.

At the switch device access level, end users must be connected to a 100 Mbit/s port. Other requirements for the device include:

• Connection via SFP to an aggregation level switch, where information is transferred at a speed of 1 gigabyte per second.
• Support VLAN, acl, port security.
• Support for security features.

According to this scheme, three layers of the network are created from the Internet provider. First, the network is formed at the level of a residential building (multi-story, private).

Then the network is “scattered” over the microdistrict, when several residential buildings, offices, and companies are connected to the network. At the last stage, a core-level network is created, when entire neighborhoods are connected to the network.

Internet providers form a network using Ethernet technology, which allows subscribers to connect to the network.

How does the switch work?


The switch memory contains a MAC table in which all MAC addresses are collected. The switch receives them in the switch port node. When the switch is connected, the table is not yet filled, so the equipment operates in training mode. The data arrives at other ports of the switch, the switch analyzes the information and determines the MAC addresses of the computer from which the data was transferred. At the last stage, the address is entered into the MAC table.

Thus, when a data packet that is intended only for one PC arrives at one or another equipment port, the information is transmitted addressed to the specified port. When the MAC address has not yet been determined, the information is transmitted to the remaining interfaces. Traffic localization occurs during the operation of the switch device, when the MAC table is filled with the necessary addresses.

Features of setting device parameters

Making appropriate changes to the switch device parameters is the same for each model. Setting up the equipment requires step-by-step actions:

1. Create two VLAN ports - for clients and for managing switches. VLANs must be designated in the settings as switch ports.
2. Configure port security, prohibiting receiving more than one MAC address per port. This will avoid transmitting information to another port. Sometimes the Broadcast domain of your home network may merge with the domain of your provider.
3. Disable STP on the client port to prevent other users from polluting the provider's network with various BPDU packets.
4. Configure the loopback detection parameter. This will allow you to reject incorrect, defective network cards, and not interfere with the work of users connected to the port.
5. Create and configure an acl parameter to prohibit non-PPPoE packets from entering the user's network. To do this, in the settings you need to block unnecessary protocols such as DCHP, ARP, IP. Such protocols are designed to allow users to communicate directly, bypassing PPPoE protocols.
6. Create an acl that denies PPPoE RADO packets coming from client ports.
7. Enable Storm Control, which will allow you to fight multicast and broadcast floods. This parameter should block non-PPPoE traffic.

If something goes wrong, then it's worth checking PPPoE, which can be attacked by viruses or fake data packets. Due to inexperience and ignorance, users may incorrectly configure the last parameter, and then they need to contact their Internet service provider for help.

How to connect the switch?

Creating a local network of computers or laptops requires the use of a network switch - a switch. Before setting up the equipment and creating the desired network configuration, the process of physically deploying the network occurs. This means that a connection is created between the switch and the computer. To do this, you should use a network cable.

Connections between network nodes are made using a patch cord - a special type of network communication cable made on the basis of twisted pair. Network cable It is recommended to purchase from a specialized store so that the connection process goes smoothly.

You can configure the switch in two ways:

1. Through the console port, which is intended for making initial switch settings.
2. Via a universal Ethernet port.

The choice of connection method depends on the equipment interface. Connecting through the console port does not consume any switch bandwidth. This is one of the advantages of this connection method.

You need to launch the VT 100 terminal emulator, then select connection parameters in accordance with the designations in the documentation. When the connection occurs, the user or employee of the Internet company enters a login and password.

To connect via the Ethernet port, you will need an IP address, which is indicated in the documents for the device or requested from your provider.

When the settings are made and the switch is created using computer network, users from their PCs or laptops should be able to access the Internet without any problems.

When choosing a device to create a network, you need to consider how many computers will be connected to it, what the speed of the ports is, and how they work. Modern providers use Ethernet technology for connection, which allows you to get a high-speed network using a single cable.