DHCP: Properties and purposes

DHCP is the abbreviation of "Dynamic Host Configuration Protocol". DHCP is a protocol which allows the server to allocate an IP Address to every client or computer on the network automatically. This means that whenever a computer joins a DHCP server, it will automatically be given an IP address. There is a lot more information which a DHCP server can provide to the client depending on the requirement of the situation. Nowadays, most of the devices are configured in a way that they automatically search for a DHCP server and asks it to allocate an IP address to it automatically. In this section we will be discussing the main purposes of DHCP as well as some technical properties associated with it. It is important to know that this process makes use of a coherent process to ensure that there is no overlapping of IP Addresses and the network runs smoothly. The main properties which we will be dealing with include Static IP Addressing, Dynamic IP Addressing, Reservations, Scopes, Leases and Options. It is interesting to know how most of the components of DHCP function collaboratively to make the system flawless.

Static vs. Dynamic IP Addressing

There are generally two ways in which DHCP servers hold the ability to allocate IP Addresses to the devices. Either they can allocate them Static IP addresses or they can provide them with Dynamic IP Addresses. The choice of the type of IP Addressing depends on the need of the situation and the type of the device under consideration. Below, you will find the details relating to both of these types of IP Addressing and you will also encounter their main uses and benefits in different situations.

According to the general method used by the DHCP, every client is allocated an IP Address automatically when it logs on to the system. However, it is important to know that these clients are allocated with a different IP Address every time they join the network. In fact, many of the computers come configured as such that they automatically ask a DHCP server to allocate them an IP Address every time they join the network. This type of IP Addressing in which the IP Address allocated to the device varies every single time is known as Dynamic IP Addressing. This type of IP Addressing is quite suitable with computers or related devices which are not quite important entities in the flow of the network and there is no problem with allocating them with Dynamic IP Addresses. Not only does it increase the accuracy of the whole process, it saves the administrators from a lot of manual effort which they might have to do.

However, devices such as servers, printer and router interfaces are quite important and it is essential that they are allocated with a fixed IP Address. This allocation of fixed IP Addresses is referred to as Static IP Addressing. This type of IP Addressing ensures that all the important and integral devices in the network have fixed IP addresses in order to avoid any problem which might occur with these devices, such as overlapping of IP Addresses. This is the reason why DHCP servers are manually allocated with fixed IP Addresses so that the whole system does not collapse due to a small issue. While the computers can bear the risk of having any related problem, servers need to be protected in every possible way to prevent the whole network from collapsing.


The allocation of static addresses to clients, servers or printers poses a problem to the whole system of DHCP. Static IP Addressing would mean that the administrator has made certain changes to the network which the DHCP server records do not recognize. In order to avoid this issue and bring all of the records on the same page, the process of Reservation has been introduced. It is a very useful and important process which makes a lot of processes simpler and more efficient.

Reservation means that the DHCP will "reserve" a particular IP Addresses for some devices. This means that every time these devices connect to the network, they will connect using the IP Addresses which have been stored for them in the DHCP server. This is done by storing their IP Address in correspondence to their MAC address, which will always remain fixed. The process of reservation is best for devices such as servers and printers on the network that required a fixed IP Address every time they connect to the network. This process will let all the control to come under the system of DHCP which will add up to the accuracy and efficiency of the system. Since no records will be manually entered into the system in this case, the whole process will become fast and more accurate due to better synchronization. In addition to this, the reserved clients will not be bound by the any time limit for which they will hold their fixed IP Address. This is because they already have a fixed IP Address in store for them so they do not have to apply again and again to renew their lease or extend their period for holding the IP Address.

In fact, the process of reservation has made a lot of things much simpler and manageable. If the system is maintained in an appropriate manner, you will surely have no problem with it. In addition to this, the amount of hard work which it saves the administrator from is also laudable.


Have you ever wondered that how do DHCP servers determine which IP Addresses are supposed to be allocated to the clients? Is the process completely random or are there still any limitations? Well, considering the complexity of various networks and the existence of colossal number of devices all over the world, the IP Addresses have to be managed in an effective way. This is the reason why the process of allocation of IP Addresses is not a totally random process. There are ranges of IP Addresses which are allocated to different organizations. It is the strict responsibility of this organization to make sure that it allocates its clients with IP Addresses from this range. For your ease, this range is given a special name, known as Scope. The scope of an organization limits the number of IP Addresses which it can provide the clients with. This not only eliminates a lot of problems, it provides a great benefit to manage and operate the whole system in an effective and efficient manner.

The size of the Scopes depends on the size of the networks for which they are assigned. For a large network, the scope will be large while for a small network the scope will also be less. The basic purpose behind the allocation of these scopes is to make sure that there is not overlapping of IP Addresses and every device is strictly allocated with a different IP Address. The problems which might occur without the existence of scopes are colossal, as in that case the IP Addresses will be duplicated and the data will not be able to find the correct path to its destination. The process of DHCP is quite useful for us, and we should us it effectively to make sure we do not encounter any issue. The process of configuration of scopes on DHCP servers is a complex task, which you will get to know at a later stage.


When a client joins a DHCP server, it is not allocated with an IP Address forever. In fact, there is a fixed duration for which that IP Address is provided to the client. Thus, the IP Address should be renewed before this duration expires. This fixed duration which is provided by the DHCP server to the client is referred to as a Lease. This lease can be thought of as a fixed contract which the DHCP makes with the client. If the client fails to renew the lease agreement before the lease has expired, he will not be able to connect to the network anymore. This strict policy has been set to make sure that everyone who has got a lease renews it on time to ensure the smooth running and efficient performance of the whole system.

It is essential to make sure that the Lease is renewed before expiry. Generally, the lease given to the clients is of 8 days. The clients, to remain on the safe side, make a request for the renewal of the lease on the 4th day so that they are not even near to the time of expiry. However, the records of the client are held in the database even one day after the data of expiry. This is done to provide a relaxation to the client who might not have been able to renew the lease due to a serious issue. You should keep in mind that the lease time depends on the size of the network. If the size of the network is large and you have to go about a number of IP Addresses, then it is logical to provide more lease time. However, if the size of network is relatively small, you should consider reducing the lease time. This process is extremely important and essential to ensure that the IP Address of each device is changed and updated on a regular basis. It is the responsibility of the client to apply for lease renewals every time.

Options (DNS Servers, suffixes)

Till now, we have basically focused on the main use of DHCP which is related to the allocation of IP Addresses to the clients and other devices. However, you are not yet familiar with many other facilities and features which the DHCP server tends to provide you with. Yes, a DHCP server is much more than a system which allocated IP Address to the devices. A DHCP server can provide you a lot of other information related to that network and its entities. Just to mention one, the DHCP server provides you the addresses of DNS servers in the network. In addition to this, it also provides the clients with the address of the main gateway which could enable them to gain access to other networks. All of these facilities are provided for the benefit of the client and to ensure that you can get all the useful information which could help you to a great extent.

Not only do you get a lot of information, you can also access a lot of settings which you can do on your system. All of this information and settings are available to you in the scope Options of DHCP servers. You can find out the most relevant information which you will need and you can use to perform your task. These extra options let the DHCP servers to stand out and provide you with an exceptionally well service. You can think of DHCP servers as a service provider which makes your work easy through its main service, but then also provides many extra features to enrich your experience and make sure that you get the best out of it.

In this chapter, we have dealt with the topic of DHCP in detail. We know that DHCP servers are very important for the automatic allocation of IP Addresses. However, we also came to know how this process can be made better to increase the overall efficiency and effectiveness of the whole system. The concept of reservation has been introduced to let you know how the problem relating to static IP Addresses can be catered and how all of the addresses can be brought under the category of DHCP servers. The concept of scopes has been defined to let you know that the process of allocation of IP Addresses is not completely random. In fact, there is a set of IP addresses from which each server should choose to allocate the clients on the network. All of these processes are in place to ensure that the process of IP Address allocation is impeccable and this great system works as efficiently as possible.

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