What is a DHCP server?

We take a closer look at how DHCP can make network administration easier

Although bring your own device (BYOD) has transformed productivity in the workplace, it's also causing headaches for IT staff as they try to ensure all devices used for work are sufficiently secured against potential hacks and theft.

One problem many admins face is the process of establishing a reliable means of connecting and managing all workplace devices to a company's network while maintaining 100% uptime. It's certainly possible to configure every device to the network by setting each IP address manually, but this is massively inefficient and a waste of an admin's time.

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It's far better to rely on what's known as Dynamic Host Configuration Protocol (DHCP), which simplifies the process by automating the assignment of IPs without impeding the security or functionality of a device.

What is DHCP?

DHCP is a network management tool that works alongside two other protocols, namely the Transmission Control Protocol (TCP) and the Internet Protocol (IP), both of which are required in order to connect devices to each other and to a network.

The main purpose of DHCP is to automate the management and configuration IP addresses across a network, so that IPs don't need to be manually assigned by an admin each time a device connects. DHCP is also responsible for the configuration of domain name server (DNS) and subnet masks, as well as default gateways.

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A DHCP server is fairly self-explanatory, in that it's the server where the DHCP is based and from which it dynamically assigns devices connecting to the network with IP addresses and configures other network information, all without much IT administrator involvement.

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In a small business or home environment, the DHCP server can simply be the router, while in a larger business it might be a single dedicated computer or server.

How does it work?

By using a client-server model, a DHCP server becomes the host, while the device connected to the network is the client. As soon as the client makes a request to the network for an IP address, the host assigns an IP address taken from a list of available options it holds. This then allows the communication between the device and the network to happen.

Main advantages of DHCP

One of the main benefits of using a DHCP server compared to other networking solutions is that it's a lot faster to set up a TCP/IP network. Additionally, it's much easier to manage such a network because there's no heavy lifting - the server automatically assigns IP addresses so IT staff don't have to.

IT staff can instead be tasked with carrying out more transformative tasks, rather than the mundane, but simple tasks that end up consuming a lot of manpower.

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Other benefits of using a DHCP network include that there are less likely to be conflicts between devices. Because the server assigns IP addresses, rather than humans, it ensures no two devices are given the same.

Other benefits include:

IP Address Management: If you decide against using a DHCP server, you'll instead need to make sure you have the resource and time to manually move clients to subnets without the need for human interaction at all. All the network information is passed to the client from the DHCP server, so no manual work is required at all.

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Centralised network client configuration: If you need a range of different of configurations for each client, you can create client groups, so each has different set-ups according to your business's requirements. All of this information is saved in the DHCP data store and this is where the configuration can be changed to roll out to all clients, without having to change them manually.

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Large network support: DHCP is especially advantageous to networks with millions of DHCP clients, as they can use the server over multithreading to process many client requests simultaneously. The server also supports data stores that are optimised to handle large amounts of data. Data storage access is handled by separate processing modules and thus enables you to add support for any database that you require.

Do I need DHCP?

You are likely to be already using DHCP protocols as a component of your home or business network as it releases you from having to assign fixed IP addresses to every new device which joins the network yourself.

Although much easier in smaller contexts, this task would be especially hard for any larger organisations that should expect hundreds of devices to be connected to a network. Each and every one of these devices would require a distinct IP address - a daunting task made even tougher with organisations without local IT teams.

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DHCP automates the process through a dynamic IP assignment - granting new IP addresses as devices join the network and, crucially, delisting them automatically once a device disconnects.

Realistically, there are very few reasons why you shouldn't be using DHCP, yet, in some cases, it could be useful to assign manual addresses. Some devices benefit from having static IP addresses, such as scanners, printers, file transfer servers, and many other devices that should always have a constant connection with a network. In such instances, a dynamic IP address, using DHCP, would require a device to update its connection settings every time it tried to communicate with the printer.

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You may encounter similar issues with DHCP if you're using machines that can be accessed remotely by staff. Assigning a dynamic IP address to a remote server may cause problems with any applications or software that rely on a static IP connection. This, in turn, requires details to be updated each time.

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Clearly, this is impractical. But even when DHCP is used across a server and network there's the option to manually assign static IP addresses to some devices - so really there's no drawback, regardless of the size of your business.

It's therefore worth taking a considered approach to what devices will benefit from static IP addresses and manually configure them, then using DHCP to take care of assigning the rest of the IP addresses, leaving you and your IT team free to carry out more interesting and innovative work.

Things to be aware of

Security Issues: Like almost anything these days, you should be aware that using DHCP automation can be a serious security risk for instance, if a rogue DHCP server is introduced to the network. This can happen if it isn't under control of the network staff, and can offer IP addresses to users connecting to the network. If a user connects to the rogue DHCP, information sent over that connection can be intercepted and looked at by unauthorised people, violating user privacy and network security, a technique known as a man in the middle attack. 

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Failure: Failure of the network can arise if only a single DHCP server is in place, as it forms a single critical junction where failure can erupt from a single issue to a system-wide problem. If the server fails, any connected computers that don't already have an IP address will try and fail to obtain one. Computers that already have an IP address from before the server's failure will attempt to renew it, which will lead to the computer losing its IP address, meaning complete network access loss until the server is restored. 

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