Bandwidth
The bandwidth of a switch is the maximum amount of traffic that it can handle. Specified in gigabits per second.
This parameter directly depends on the number of network ports in the device (excluding Uplink). Actually, even if the bandwidth is not given in the specifications, it can still be calculated using the following formula: the number of ports multiplied by the bandwidth of an individual port and multiplied by two (since both incoming and outgoing traffic are taken into account). For example, a model with 8 Gigabit Ethernet connectors and 2 SFP ports will have a bandwidth of (8*1 + 2*1)*2 = 20 Gbps.
The choice for this indicator is quite obvious: you need to evaluate the expected traffic volumes in the serviced network segment and make sure that the switch's bandwidth will cover it with a margin of at least 10-15% (this will give an additional guarantee in case of emergency situations). At the same time, if you plan to often work at high, close to maximum, loads, it will not hurt to clarify such a characteristic as the internal bandwidth of the switch. It is usually given in a detailed technical description, and if this value is less than the total throughput, serious problems may arise under significant loads.
MAC address table size
The maximum number of MAC addresses that can be stored in the Switch's memory at the same time. Specified in thousands, for example, 8K — 8K.
Recall that the MAC address is the unique address of each individual network device used in physical routing (at layer 2 of the OSI network model). Switches of all types work with such addresses. And it is worth choosing a switch according to the size of the table, taking into account the maximum number of devices that are supposed to be used with it (including based on the possible expansion of the network). If the table is not enough, the switch will overwrite new addresses over the old ones, which can noticeably slow down the work.
Gigabit Ethernet
The number of standard Gigabit Ethernet RJ-45 network connectors provided in the design of the switch.
As the name suggests, these connectors provide data transfer rates up to 1 Gbps. Initially, Gigabit Ethernet was considered a professional standard, and even now the real needs for such speeds arise mainly when performing special tasks. Nevertheless, even relatively inexpensive computers are now equipped with gigabit network adapters, not to mention more advanced technology.
As for the number of connectors, it corresponds to the number of network devices that can be connected to the "switch" directly, without the use of additional equipment. In the case of Gigabit Ethernet, the number of connectors up to 10 inclusive is considered relatively small, from 10 to 25 — average, and the presence of more than 25 ports of this type is typical for professional-level models. At the same time, it is worth noting that in some "switches" individual connectors of this type are combined with optical SFP or SFP + (see below). Such connectors are marked "combo" and are taken into account both in the RJ-45 count and in the SFP/SFP+ count.
SFP (optics)
The number of optical network ports of the SFP standard provided in the design of the switch. We emphasize that we are talking about "ordinary" SFPs; SFP+ data is usually listed separately.
Specifically, in switches, the marking “SFP” usually means a connector for fiber with a connection speed of 1 Gbps. Technically, this is not much compared to RJ-45 speeds; however, this connection format has a number of advantages. One of the main ones is a greater effective range: the mentioned gigabit standard used in switches works with a cable length of up to 550 m, and by the standards of fiber, this is still very little. True, the cable itself is sensitive to kinks and requires quite delicate handling; on the other hand, it is completely immune to electromagnetic interference. On the other hand, in general, the SFP format is noticeably less popular in network equipment than RJ-45; therefore, there are few ports of this type even in advanced devices. So, solutions for
2 or
4 SFP connectors are most widely used, although there are more - 6, 8, or even 10 or more. It is also worth considering that the so-called combo connectors can be used in switches, combining SFP and RJ-45; the presence of such ports is specified in the notes, they are taken into account both in the calculation of RJ-45 and in the calculation of SFP.
To clarify, Uplink inputs also often use this type of connector; however, their
...number is specified separately (see below).Basic features
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DHCP server. A feature that makes it easy to manage the IP addresses of devices connected to the switch. Without its own IP address, the correct operation of the network device is impossible; and DHCP support allows you to assign these addresses both manually and fully automatically. At the same time, the administrator can set additional parameters for the automatic mode (range of addresses, maximum time for using one address). And even in fully manual mode, work with addresses is performed only by means of the switch itself (whereas without DHCP, these parameters would also have to be specified in the settings of each device on the network).
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Stacking support. The ability to operate the device in stack mode. A stack consists of several switches that are perceived by the network as one “switch”, with one MAC address, one IP address, and with a total number of connectors equal to the total number of ports in all involved devices. This feature is useful if you want to build an extensive network that lacks the capabilities of a single switch, but do not want to complicate the topology.
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Link Aggregation. Switch support for link aggregation technology. This technology allows you to combine several parallel physical communication channels into one logical one, which increases the speed and reliability of the connection. Simply put, a switch with such a fun
...ction can be connected to another device (for example, a router) not with one cable, but with two or even more at once. The increase in speed in this case occurs due to the summation of the throughput of all physical channels; however, the total speed may be less than the sum of the speeds — on the other hand, combining several relatively slow connectors is often cheaper than using equipment with a more advanced single interface. And the increase in reliability is carried out, firstly, by distributing the total load over individual physical channels, and secondly, by means of "hot" redundancy: the failure of one port or cable can reduce the speed, but does not lead to a complete disconnection, and when the channel is restored, the channel is switched on automatically.
Note that both the standard LACP protocol and non-standard proprietary technologies can be used for Link Aggregation (the latter is typical, for example, for Cisco switches). In addition, there are quite a few alternative names for this technology — port trunking, link bundling, etc.; sometimes the difference is only in the name, sometimes there are technical nuances. All these details should be clarified separately.
— VLAN. Support of the VLAN function by the switch — virtual local area networks. In this case, the meaning of this function is the ability to create separate logical (virtual) local networks within the physical "local area". Thus, it is possible, for example, to separate departments in a large organization, creating for each of them its own local network. The organization of VLAN allows you to reduce the load on network equipment, as well as increase the degree of data protection.
— Protection against loops. The switch has a loop protection function. The loop in this case can be described as a situation where the same signal is launched in the network in an endless loop. This may be due to incorrect cable connection, the use of redundant links and some other reasons, but anyway, such a phenomenon can “put down” the network, which means it is highly undesirable. Security prevents loops, usually by disabling looped ports.
— Limiting the speed of access. The ability to limit the data exchange rate for individual switch ports. Thus, it is possible to reduce the load on the network and prevent the "clogging" of the channel by individual terminals.
Note that the matter is not limited to this list: other features may be found in modern switches.PoE outputs
The number of PoE-enabled outputs (see above) provided in the design of the switch. This number corresponds to the maximum number of PoE network devices that can be connected to this model at the same time.
Total PoE power
The total output power provided by the switch when powering devices using the PoE standard (see above).
This indicator usually corresponds to the sum of the powers of all outputs — that is, the power of one PoE port, multiplied by their total number. However, the power limits for one output and for the entire switch are somewhat different: if a load with a power equal to the output power of the power supply on this connector can be connected to a single connector, then the total power consumption of all devices connected via PoE should ideally not exceed 75% of the total power supply — this gives an additional guarantee in case of malfunctions. In fact, this means that all PoE outputs cannot be used “to the fullest” at the same time. For example, if there are two such outputs, and one is loaded at 100%, then the second can be loaded with a maximum of 50% — the total power consumption in this case will be the same 75% of the total output. Therefore,
a large total power is needed when using the device to the maximum.
PSU
— Built-in.
The built-in power supply does not take up space on the outside, but can significantly increase the size and weight of the entire switch. Because of this, this option is quite rare — mainly among rack-mount models (see "Form factor"), where an external unit can create significant inconvenience, as well as among the most powerful desktop switches, for which restrictions on dimensions and weight is not critical.
— External. Theoretically
, an external power supply requires additional space, and therefore is not as convenient as an internal one. In fact, most blocks of this type are quite compact in size and are equipped with “plugs” for sockets right on the case — in other words, the block is installed on a socket, and from there the wire stretches to the switch. And the absence of power circuits and transformers inside the case has a positive effect on compactness. Thanks to all this, this option is very popular among desktop models (see "Form factor"), primarily entry-level and mid-level.
— No BP. The absence of a power supply both in the design and in the delivery set is a rather rare case found in three types of switches. The first variety is models that use PoE power (see above) and do not require separate power sources. PoE power is relatively small, so relatively simple devices with a small number of ports fall into this category. The second variety is professional switc
...hes, the power supplies for which are sold as separately installed internal modules; such equipment may even provide the possibility of using two PSUs simultaneously (main and backup) and hot-swapping them. The third type — switches with installation on a DIN rail (see "Form factor") and having terminals for connecting a specialized external power source.Supply voltage
The amount of voltage required by the switch for uninterrupted operation. The power supply voltage of network equipment can vary from 5 V to 230 V, which allows you to power compatible devices from either a low-voltage USB socket on your computer or a standard household outlet. Values in the middle assume that the switch is powered by the appropriate power supply.