A simple switch for computer consoles on a transistor and relay (KVM Switch). How to connect a KVM guest to the Internet using a wireless network Connecting kvm to servers

KVM switch cascading refers to the way additional KVM switches are connected to the main switch. The purpose of this procedure is to increase the number of ports for connecting servers and organizing access to control them from one or several consoles (KVM console - Keyboard, Video (monitor), Mouse). Often this possibility of expanding the control system big amount servers are called scaling.

It is theoretically possible to connect any KVM switches, but for full, convenient and correct operation, they must be compatible, and therefore:

the lower menu should be embedded in the upper KVM switch menu,
KVM switches must have the same interface,
must have the same functionality.

Cascading makes sense when extending access with regular KVM switches (not IP KVM). In turn, IP KVM switches are combined into unified system with centralized control using specialized software.

When cascading, KVM switches of the first level can be switches with an integrated control console (Keyboard Video Mouse) or an IP module; workplace operator (point of entry or access to the system). However, to integrate IP KVM under control from a single console in a single room (eg, data center), ATEN has provided a higher level switch called Matrix KVM.

Cascading switches

Cascade - Connect an optional KVM switch with port loss. With this option, the console port of the second level switch is connected to one of the ports for connecting computers (CPU port) of the KVM switch. This connection is usually made with an interface cable used to connect computers. It is possible to connect up to three levels, when the console port of the third level switch is connected to the "CPU port" (in ATEN devices this is the name of the port for connecting a computer or server) of the second level switch.

Wiring diagram for cascading ATEN switches.

In this diagram, the first level is the switch to which the console is connected (Keyboard Video Mouse). The switch of the second level is connected through the console port of the second and occupies one CPU port in the first, similarly the third is connected to the second.

Diagram of the maximum cascade connection of ATEN KVM switches using the example of CS9138.

With this connection, the maximum number of connected servers is 512 when using 73 ATEN CS9138 KVM switches. When I manage so many servers, it is simply impossible to keep in memory what is connected to what and through which port in which chain the KVM operator console can be connected to the KVM server interface. To solve this problem, ATEN has provided the possibility of embedded menus.

The figure shows the OSD menus of the ATEN CS9138 KVM switch.
Left - no cascading left,
On the right - after connecting an additional KVM switch to the second port of the first CPU.

The KBM switch menu has a tree structure. The photo on the right shows how the ports of the second switch are displayed in the menu of the first. You can assign server names to the CPU ports. Using the menu, you can set various modes of the switch, for example, enable automatic scanning of only active ports. Using the menu, you can directly connect to the control console required computer from the third level in a cascade.

Connecting switches with a loop (stack)

Daisy Chain connection to the stack - the connection of switches of different levels occurs via special cascade ports and special daisy cords (Daisy Chain). With this connection on the switch, the connection port of the CPU computer remains free, and the console ports of the lower-level switches are disabled. On the switches in the indicator window, the number corresponding to the switch level lights up.

ATEN KVM Switches Daisy Chain Diagram

With the correct selection of compatible KVM switches for cascading in the menu of the top-level switch, in the form of a "tree", the menu of the lower-level switch is embedded.

ATEN has provided the ability to stack KVM switches on some of the switches. Dedicated ports and a shelf cable are used to connect the switches.

Switches integrated with KVM console and IP KVM only have an output port. The rest of the switches have two input and output ports. The switch of the first level turns on the KVM console, and in the switches of the lower level, when connected by a daisy chain to the upper ones, the console ports are disabled. The shelf connection allows up to 32 KVM switches to be stacked. When connected, depending on the position of the switch in the stack, the indicator displays its number in the stack.

Indication of positioning of switches in a stack.

The OSD menu of the KVM switch is built sequentially one below the other and looks like shown in Fig. The first position corresponds to the device number in the stack, the second to the port number on the device. As in the previous version, you can set the server name and, if necessary, make a quick transition to any server.

On the left is the OSD menu of the KVM switches installed in the stack.

Mixed cascading.

Developing the direction of KVM switches, ATEN proposed a solution to the problem of administering a large number of servers by a group of operators according to the scheme any to any or to a closed group.

To meet this challenge, ATEN offers Matrix Switches with truly huge server management access system scalability.

Mixed connection scheme for IT devices (servers, network switches, etc.).

When cascading into a stack with a loop up to 8 levels, you can get non-blocking access to 256 ports. At sharing daisy chain and cascade connection, the system allows 9 administrators to provide access to thousands of servers.

Although the last connection option is able to solve the problem of almost any data center (sony of thousands of KVM ports), it still has limitations in comparison with the use of the CC2000 software product.

The CC2000 Centralized Management System allows an unlimited number of devices located anywhere in the world to be united under a single control, but that is another story.

The need to control several computers at once from one set of keyboard and mouse often arises in working conditions. This is what is used for KVM switches("Keyboard, Video, Mouse"). In recent years, such switches have been replaced by numerous programs that allow you to do the same through local area network or the Internet, but switches are still used where maximum reliability is needed - the software can sometimes fail.

KVM switches are used both in offices (desktop models) and in server rooms (server rack models). Finding the right model is not as easy as it seems at first glance.

In the next section, we will look at the most important features of KVM switches, and then present to your attention several models that can be purchased in our catalog stores.

Key features to look out for

The scope of its application depends on the design of the switch housing. For offices, they buy desktop models that do not take up much space and are designed for 2-4 machines (both ordinary PCs and servers that are not in a rack).

KVM-over-IP - switches that allow you to control a PC via the global Internet. This is a separate category that has not been so popular lately due to the fact that such functionality is in the servers themselves.

A KVM extender is two devices (one on the computer side, the other on the peripheral side) that allow you to control it remotely, but not over the Internet or a local network.

The KVM console is a special device for server rooms that when folded takes up 1U in a rack. In the unfolded state, it is a screen, keyboard and touchpad (or other device that replaces a mouse).

Also, the most powerful and multifunctional switches are installed in server racks - for 8 or more machines. They do not have a screen and keyboard - to connect them, the server cabinet must have additional shelves.

Number of connected computers

The main characteristic of any KVM switch. How more computers you can connect to it, so it will cost more, and the dimensions of the device will be larger. If you are looking for a model for an office, then 2 or 4 connections will probably be enough (the ports to which computers are connected are called "console"). If it comes when used in a server room or server room, there is no limit.

Supported Monitor Resolution

Be sure to make sure that the purchased switch supports the resolution of those monitors that will be used in conjunction with it. With modern models, this problem disappears, but note that switches are not designed for monitors. high resolutions(for example, 4K).

Console connections

First of all, you need to determine which computers with which video outputs will connect to the KVM switch. It can be VGA (analog and legacy; maximum resolution - 1280x1024 pixels), DVI (digital; up to 1920x1080 pixels), DisplayPort or HDMI (digital; up to 2560x1440 pixels).

Then you need to pay attention to the ports for the keyboard and mouse. The best option is USB, but if your server or computer has PS / 2 ports, these will work too. Please note that most of the models do not work with wireless peripherals.

More advanced and expensive KVM switches allow you to connect not only computers, but also other devices - printers, audio devices, modems, removable drives, and so on. It uses USB ports, 3.5mm audio outputs and audio inputs, as well as a variety of interfaces such as RJ-45 or RS-232.

Control and indication

Typically, the switch is controlled by a single button on the case or on the remote control, which alternately changes the active console port. More advanced models have separate buttons for each port. Special indicators indicate the port that is active at a particular moment.

Nutrition

KVM switches are classified as either passive or active based on power type. Passive models are powered by the keyboard and mouse interfaces. Sometimes they may simply not work due to lack of power, but in recent years this problem has been extremely rare.

Active KVM switches use their own power adapter that comes with the kit. This is a more reliable, but also more expensive option - only server switches are usually equipped with their own adapter.

If you are already using personal computer, then you have to periodically update not only software, but also "hardware", that is, the computer itself. What to do with the old one? Especially if only the system unit remains of it (the monitor has "moved" to a new one). The "486DX33" acquired ten years ago, which was then the latest technological achievement, is now impossible to sell.

And it's a pity - after all, during his long (by computer standards) life, he managed to grow microcontrollers and EPROM programmers, it has (and work well) various radio amateur and radio programs. That's just, it is not suitable for working on the Internet (that's why a new one was purchased).

It is problematic to install all this "architecture" on a new one - there are not enough COM and LPT ports (the old one had three COM and two LPTs), and with USB ports nothing new from the old periphery can work. So it was decided to keep two system units and two "mice".

And switch between the monitor and the keyboard. Moreover, for these purposes, there are (disgusting, as it turned out) workplace switches on sale.

The purchased mechanical switch of workplaces "Maxtro" worked for no more than a month. Then the "freaks" began - either the keyboard does not work correctly, or not all the colors are displayed on the monitor. You have to push the handle all the time, push it in order to catch the moment when everything will work normally.

After prolonged torment with him, it was decided to make a homemade switch of workplaces, but not on a Taiwanese "biscuit", the contacts of which simply peeled off, but on the Soviet relay RES-22, controlled by two buttons.

Surprisingly, "Maxtro" switched all the contacts of the keyboard and monitor connectors, which is why there were so many contacts in it. In fact, seven contact groups are enough for such switching, because all "GNDs" can be connected together, and the keyboard power can be switched with two diodes. Each RES-22 has four contact groups, therefore, even one of them remains, which can be used to control the relays themselves (trigger effect of the relay).

Schematic diagram

The circuit is made in such a way that it recognizes the switched on computer 2 by the arrival of the +5 V supply voltage from it to the keyboard. If you turn on computer 2, then the + 5V voltage will go through the capacitor C2 to the base of the transistor VT1, which will open and turn on the relay.

It is self-blocked by the free contact group K1.4 and after the end of charging C2 it will remain on. In this state, the keyboard and monitor will switch to computer 2. In the de-energized state, the keyboard and monitor will switch to old computer 1.

Rice. 1. Schematic diagram switch consoles.

All parts are assembled in an iron case from the "Maxtro" switch. "Mice" are used separately for each of the computers. The switch is powered by network adapter from a faulty printer.

The problem of switching a printer between two computers is solved differently. The printer (Samsung 1210) has two ports - LPT and USB. LPT port connected to old system unit, and USB to new.

With the advent of broadband Internet to offices, full-fledged remote administration became possible. Thanks to this technology, service organizations were able to significantly reduce the response time to a client's request, and system administrators got the opportunity to provide support even outside the office. But the remote administration tools work only after the OS boots, if for some reason it is impossible to require the physical presence of a specialist. Switches can solve this problem. KVM over IP.

Probably all administrators know what KVM switches are, this is a device that allows you to use one console (monitor, keyboard and mouse) to control several PCs. KVM switches can be as simple as personalized:

So for rack mounting, supporting cascading and allowing you to manage a large number of servers at once (up to several hundred) from one place:

KVM over IP switches stand apart in this company, allowing you to access the PC console from anywhere using the TCP / IP protocol. For a long time, these devices were considered "luxury goods", but recently offers have appeared on the market at a very humane price, making them quite affordable for small organizations.

Let's consider the capabilities of the KVM over IP switch using an example ATEN ALTUSEN KH1508i worth 727 USD. Besides an attractive price this device allows control of up to 256 PCs (with cascading switches), supports PC, Mac, Sun platforms, PS / 2 and USB connections to PCs.

The switch is designed in 1U format and can be mounted in a rack. On the front panel there are output switching buttons, an active port indicator, a connector for updating the firmware, a power indicator and a Reset button.

Another feature of the switch is the use of UTP 5e twisted pair cable to connect controlled PCs, which allows them to be placed at a distance of up to 40 m. laying of expensive specialized cables. Connectors for controllable PCs, network, slave switches and console are located on the back of the switch:

To connect controlled PCs, client modules that emulate the necessary peripherals are used. Emulation is performed directly by the module, regardless of the presence of a control device. This means that if you forget to turn on the switch, the controlled PCs will still detect the keyboard, mouse and monitor at boot time and you do not have to restart them in order to gain access.

The manufacturer offers a wide range of client modules for controlling computers of different platforms; two types of client modules are available for PCs: KA9520 (PS / 2) and KA9570 (USB), costing 71 USD. Each module is a controller with an RJ-45 interface and a half-meter cable with VGA and PS / 2 (USB) connectors, has its own firmware that is regularly updated by the manufacturer, there is a switch on the module case that switches it to the firmware update mode. The KA9520 module is shown below:

For mounting on a vertical surface, a special basket is supplied with the module.

Switch settings are made via the on-screen menu or the web interface (to a somewhat limited extent). If you do not have Mac computers or Sun, then all settings will be accessible via the web (by default, all switch ports are configured for the PC platform).

The connection to the device is made via a secure HTTPS protocol despite the fact that the switch accepts connections on port 80, it still redirects to a secure connection (port 443). To transfer data between the switch and the client program, port 9000 is used, this should be taken into account when forwarding ports (i.e., in addition to 80 and / or 443, you also need to forward 9000).

Let's move on to network functions switch, by default it is configured to receive settings via DHCP, which, in our opinion, is much better than the preset IP, just look at which address is assigned to the device in DHCP settings server and reserve it for the corresponding MAC address (indicated on the device case).

For access, you can use any browser (optimally IE), the web interface is not rich in settings, you can run Windows (only through IE) or a Java client, or download them if you cannot run them through the browser in any way.

The parameter deserves special attention Network transfer rate, for comfortable work with the device, there should be specified the minimum guaranteed speed of the channel through which the switch is accessed.

To access the managed PCs, you need to start the client. We were unable to run Windows Client on Windows 7 64-bit, in this case a Java client that works on any platform with Java support helps out. Already in the client we can produce more fine tuning devices:

To switch to managed devices, use the tab Main, which displays all client modules connected to the switch (or chain of switches):

At correct setting baud rates work through remote client quite comfortable, the only drawback is some (sometimes significant) lag of the mouse cursor on the remote system from the cursor on the control PC.

However, it should be remembered that work via KVM Over IP is required for the most part when emergency situations when control is required at the PC load level, in other cases it will be much more comfortable to work via RDP. If you are using a USB module (KA9570), please make sure the BIOS has enabled USB keyboard and mouse support to avoid any unpleasant surprises.

We also recommend that you configure the server BIOS to turn on by a signal from the keyboard or over the network. This will allow you to remotely turn on the server if you suddenly turn it off by mistake or someone from overly diligent employees turns it off.

KVM over IP switches allow an administrator to get almost complete control over a controlled PC from anywhere in the world, if there was Internet access. And the seemingly relatively high price of the device at first glance is more than compensated by the provided capabilities. Either way, it's worth considering what is cheaper, a KVM IP switch, or the plant downtime required for a technician to arrive.

KVM over IP - what is it?

KVM(or kvm over ip) is a device that allows video and mouse / keyboard input to be transmitted over a network using an IP protocol from your server. With KVM, you can reboot the server, access the server BIOS and other functions that cannot be performed on the server through the terminal. You can activate KVM access for free on the service page.

KVM is free for the first two hours a day. The fee for the subsequent KVM connection is 30 minutes - 300 rubles.

How do I connect KVM to a server?

Ready! You will get KVM access to the server for the selected period of time (up to 2 hours). Within 15-20 minutes, access will be sent to the contact e-mail.

KVM doesn't work

Work through utilities

When working through utilities, there is no need to configure Java.
To manage KVM, Windows users can use the following utilities:

CN8000 WinClient
- for KVM from ATEN manufacturer;
- for KVM from ATEN manufacturer;
KVM Vision Viewer - for KVM from other manufacturers.

Working in the browser

To work with KVM, the browser must support Java. Opera and Chrome browsers (starting from Cromium 42) and Firefox Standard (versions above 52) no longer support Java. Of the browsers being updated, Java support is available in Firefox ESR (up to March 2018).

The web interface for KVM CN8000A models is guaranteed only in browsers based on the Gecko engine (for example, FireFox). Webkit (Chromium and based on it) may experience display issues. In this case, we recommend using Windows or Java clients.

If the KVM console has a black screen, the inscription "No Signal"

In case of prolonged inactivity, the screen will be turned off (“No Signal” will appear), to resume, you must press any key in the console (we recommend pressing “Alt” or “Ctrl” instead of “Enter” to avoid executing the command typed in the console earlier).

Keyboard not working in KVM console

Try resetting your KVM device. To do this, log in to the KVM web interface, go to the "Maintenance" section and perform a reset. Usually this item is called "Unit Reset", "Reset USB". 2 minutes after the reset, check the keyboard operation in KVM.

What to do if KVM window in Java won't open

If the KVM window does not open for a long time, check if Java is installed on your PC. Go to the Java official website, then click on the link “Is there Java software installed on my computer? ". If Java is installed, then follow the instructions below.

If Java version 8 is installed

To start the KVM console, you need to complete three steps:

1.
Make changes to the file java.security... The file is located at JDK_HOME / jre / lib / security / java.security, usually these are the paths:
for Windows OS:
C: \ Program Files \ Java \ jre1.8.0_91 \ lib \ security for 64-bit versions of JAVA, or
C: \ Program Files (x86) \ Java \ jre1.8.0_91 \ lib \ security for 32-bit versions.
for Linux OS:
/usr/lib/jvm/java-7-openjdk-amd64/jre/lib/security/java.security
or you can find the file with the command in the Linux console:
find / usr / lib / -name java.security
In this file, you need to comment out the line that begins with:
jdk.certpath.disabledAlgorithms
those. add the "#" character at the beginning of the line, for example:
# jdk.certpath.disabledAlgorithms = MD2, RSA keySize
Note that to edit the file java.security need to run text editor as administrator (for Windows) or superuser root (for Linux).

In case the problem persists, try installing Java 7 and setting the security level to Medium (see above).

If the above methods did not help you and any error messages appear when opening the KVM window, you should refer to the official JAVA manual on the developer's website: http://java.com/ru/download/help/

Try using Windows and Internet Explorer version 9 as a solution.
It is also possible to work in Linux systems x32 at using Firefox and 7 version of Java.
Additionally, you can use the emulation mode of old browsers in Internet browser Explorer 11 (accessible by pressing F12).

What to do if a Java KVM window opens from the browser, but there is an error in the status bar?

Information about messages about blocking Java in the browser is posted here.

What is IPMI and why is it needed?

IPMI- interface for remote control server. It is designed for autonomous monitoring and control of functions built into the server hardware.

IPMI works independently of the operating system on the server. Therefore, if the processor / BIOS / operating system encounters problems, you can reboot the server, restore critical management, logging and inventory functions via IPMI. You can read more about IPMI on the thematic forums.

Accessing the IPMI interface

If you have a problem with displaying the console and IPMI accessibility, use the instruction:. In case of difficulties, write.

Installing the operating system using IPMI

You can install the operating system yourself using IPMI. The IPMI interface allows you to remotely install the OS and mount the image file as a virtual DVD-ROM on the server.

The following images are available to boot into IPMI:

Centos 6, 7;
Debian 8, 9;
Ubuntu 14, 16, 18;
ESXI 6.5, 6.7;
SystemRescueCd 5.3.2.

If you need to download another image, write with a link to the image.

To install the operating system, follow the steps:

3.
On the Manage tab, click IPMI console:
4.
On the first transition confirm launch:
- in the first pop-up window, check the box next to "Always trust content from this publisher" and click Run:
- in the second pop-up window, click the button Yes:
5.
In the "Web IPMI" window, select Virtual media — Virtual storage:
6.
In the "Logical Drive Type" field, select the type of image ISO File, in the "Image File Name and Full Path" field, select the file with the distribution kit (any .iso file), click Plug in, Further OK:
7.
Reboot the server in the console window Macro — Macro — Ctrl + Alt + Del:
8.
After that, the "Virtual DVD" device will appear in the server BIOS, which can be set first in the order of loading disks ( Boot priority):
9.
Save your changes by selecting "Save changes and exit" in the "Exit" menu:
10.
Boot from the virtual DVD and install the operating system.

If you have a problem with displaying the console and IPMI accessibility, use the instruction:. If you have any difficulties, write.

It's important to know

The IPMI controller forwards to motherboard virtual DVD-ROM and USB keyboard control, so you cannot turn off support for USB devices in the BIOS or OS.

What if IPMI doesn't work?

Ways to solve IPMI console display problems (for example, black screen):

Press any key on the keyboard (for example, Shift). If the keyboard does not work, use the virtual keyboard.

For a server with operating system Ubuntu - press keyboard shortcut Ctrl + Alt + F1.

Restart IPMI (cold reset) by connecting to the server via SSH as root and issue the command: ipmicfg -r or ipmitool bmc reset cold.

The ipmitool utility requires some kernel modules, you can enable them with a command in the server console as the root user: modprobe ipmi_si && modprobe ipmi_devintf && modprobe ipmi_msghandler.