DHCP is what? DHCP settings, options and configuration. How to enable or disable DHCP?

It is well known that to work with the network every device, be it a computer, laptop, tablet or phone, must have a certain electronic identifier - IP-address, as well as configured mask, gateway and DNS server information. This address network interface when connecting immediately trying to get from the special equipment that deals with automatic distribution of addresses. If such equipment is not available, then the user must enter the network parameters manually. If there are many computers on the network, there may be errors in addressing and duplication of addresses, leading to system failures and a slowdown in overall network performance. In the home network, in the absence of automatic distribution of addresses, you must register the network settings manually on each device to connect, for example, to the router. Not every user has enough knowledge and experience to correctly change such settings. Therefore, at home, too, many users try to deploy automatic distribution of addresses, that is, deploy a DHCP server.

DHCP is what?

We will deal with this issue. To avoid addressing errors, Dynamic Host Configuration Protocol (DHCP) was implemented. This is a function that dynamically distributes network settings to connected client machines. If these settings have the option "to receive an IP address only from a DHCP server" on the devices and the DHCP service is enabled, then all responsibility for correctly configuring the network settings on client computers is transferred to the DHCP server. This significantly reduces the cost of support and management of the network, and helps to avoid errors in the distribution of addresses. A service that includes DHCP is automatically started by default when any device that supports wired or wireless interfaces is turned on. For example, on tablets or phones, it's enough to turn on Wi-Fi and find your own and connect to it among the found devices that distribute the Internet. In this case, automatic allocation of addresses eliminates duplication of IP and, as a result, helps to avoid network conflicts.

How the distribution of addresses occurs

During the connection of any client device to the network, a special broadcast request is sent to the network in order to search for the distributing parameters of this DHCP server network. What kind of server is this and what is it important for a large network? This is the name of the device that is responsible for distributing addresses to computers on the network for automatic use on different clients. If such a server is present, it creates a packet with a response to the client request, which can include such settings as IP address, network mask, gateway parameters, DNS server addresses, domain name, etc., and sends this packet to the client device . The client receives a confirmation signal from the DHCP server. The generated data package is standardized, so almost any operating system can decrypt it and use it.

Parameters issued by the server for the client device have a limited customizable expiration date, which has its own name - "lease time". Addresses issued by the server are analyzed for matching with valid addresses with unexpired lease time, so duplication of addresses is excluded. Usually the lease term is small - from several hours to 4-6 days. After this period the device repeats the request to the server and receives from it the same address (if it is still free) or any free one.

Client settings for automatic network settings in Windows OS

In order for the client to receive the response network parameters from DHCP, it is necessary to check several settings in the Control Panel of the computer (considered on the example of the Windows operating system ). To do this, go to the Start menu, then - to the Control Panel (which must be switched to the classic view) and select the "Network Connections" item. Choose the network connection that is planned to work with DHCP, click on it with the right mouse button and go to the "Properties" item. In the window that will open, go to TCP / IP Internet Protocol Properties. DHCP is what? This is the receipt of automatic network parameters. Therefore, we mark the options with points to automatically obtain the IP address and DNS. Having made a choice, click "OK". The DHCP configuration on the client is complete. Now the device will receive the address from the DHCP server automatically when Windows starts.

The DHCP configuration in Windows 7 is similar, but the location of the adapter properties is slightly different from Windows XP. Just go to Start - Control Panel - Network and Sharing Center. Select "Change adapter settings" in the left menu. Next - similar to the above on the settings in Windows XP.

Configuring automatic distribution of addresses in other operating systems

On Linux or Android devices, the connection is not a problem when the DHCP server is deployed on the network. It is enough just to turn on the network interface (wired or wireless), wait for the data exchange between the device and the DHCP server to pass and make sure that the network settings are received and applied successfully. DHCP services are enabled by default on almost all devices.

If the connection does not occur, then you need to check the status of the automatic reception of addresses. For example, on Android OS it is necessary to go to Settings - Wireless networks - Wi-Fi settings - Advanced and make sure that the option "Use static IP-address" is disabled.

Data sent by DHCP

DHCP options are parameters that are passed from the server to the client. All these transmitted parameters are divided into categories. There are mandatory options, such as IP address and network mask. There are unconfigured service options, which, for example, show the beginning and the end of the options in the transmitted packet. Essentially, the options are typical value-key pairs that can be seen and configured in security policies.

The main parameters of DHCP in the package, except for the IP address and mask, are 3 (Gateways), 6 (Domain Name Servers), 44 (NBT Name Servers), 46 (NBT Node Type). These parameters are group, that is, they can have several values. For example, there may be more than one gateway or DNS server address. The options are configured in the DHCP server settings.

DHCP server settings

Before configuring the settings, several basic DHCP options must be calculated. What kind of options are these? - you ask. Options are all those network parameters that are transmitted from the server to the client. The two main options are the range of addresses being distributed and the subnet mask. The entire range of organization addresses is usually divided into several segments designed for various tasks, such as telecommunications, static server addresses, etc. To prevent static addresses from being involved in the distribution, creating additional load on the server, the ranges of addresses being distributed can be limited. For example, for the operating range 192.168.1.1-192.168.1.254, the addresses from 1 to 10 can be defined for communication, 11 to 30 for the server, and for DHCP, the range from 31 to 254. That is, any server address given to the client, Will lie only in this range. Also, you can configure the allocated range of the exception address, and they will not be distributed to the client devices either.

Next, before setting up a DHCP server, you need to decide which options it will still distribute. Is it necessary to distribute, for example, gateway or DNS parameters. After that, the data is entered on the server, its activation is started and the server starts distributing addresses.

Home DHCP server

At home, routers are often used as a DHCP server. The content received from the provider is distributed to home appliances - computers, laptops, telephones, televisions and other devices connected to the network by wire or wireless. This creates something like a virtual server that distributes addresses to users. From the outside, it looks as if one user has opened several pages in his browser on one of his computers. In this case, only one router is connected to the external network. This allows you to significantly save on the number of connected lines.

Configuring Automatic Routing on the Router

To configure automatic distribution of addresses to home devices, you must connect the router to the computer (laptop) with a network cable. In any browser, write the address of the router (usually 192.168.0.1). In the suggested login and password request fields, enter "admin" by default (this data is often specified in the router's operating manual). As a result, we will see the router settings menu . We go to the Lan or Network sections (the names can be different) and find the submenu with the DHCP settings. How to enable the distribution of addresses on the router? Simply put a tick in front of the enable DHCP line and reboot the router.

Configuring the DHCP Router

If the default settings do not suit, you can change the configuration of the parameters. In the same menu where we turned on the address distribution function, you can enter the range of IP address distribution, for example 192.153.0.1 - 192.153.0.3. For work, you can specify only two addresses, for example, for a laptop and mobile phone. This limits the number of concurrent devices, which is the simplest connection protection.

Next, configure the gateway (Gataway). This is the IP address of the device through which the Internet passes for devices. Usually this parameter is the same as the IP address of the router.

Having created the basic settings, you need to save them and reboot the router. Immediately after the reboot, the settings will take effect.

Before disabling DHCP, you need to make sure that the devices have static addresses. To disable automatic distribution, you must uncheck the DHCP option in the router settings, save changes and reboot the device.