DHCP What is it, what is it for and how does this protocol work?

DHCP or also known as dynamic host configuration protocol specializes in simplification and improvement of the accuracy of IP addressing . In this way he has the ability to network devices quickly and easily, making it an essential method of ensuring that devices can be my en network and correctly configured.

Therefore, this protocol aims to be able to Dramatically reduce the errors that occur when IP addresses are assigned manually. In addition, they also have the option of keep IP addresses individually . In this way, this protocol is one of those in charge of allowing any operate correctly, quickly and easily .

Considering the fact that this tool is not well known to everyone and it is also not a term widely used by people, here we will explain a little more what are these protocols, what they are used for and how they work in computing. To do this, follow in detail everything we will teach you in this post.

What is a DHCP server and what is it used for in computer networks?

These servers are those that allow a computer connected to a network of pouvoir get its configuration dynamically . In addition, it is a network protocol used in IP networks where a DHCP server is responsible for automatically assigning an IP address and other information to each host in the network. All of this allows you to communicate effectively with others terminals .

In this way, the main objective of this tool is to simplify network administration. Likewise, it works to be able to distribute the IP addresses of a network, and for assign subnet mask , the address of domain name server DNS , the default gateway address and many others configuration settings relevant.

This is how this server has a dynamic IP address list and assigns to customers as they become free , taking into account at all times the customers , promising were in possession of these PIs, when they used them and who they are. subsequently assigned . This allows customers on a IP network to be able to get their configuration settings automatically .

How does DHCP interact with other Internet protocols?

The DHCP server is the one who is responsible for the distribution of IP addresses , it will therefore be the basis of all DHCP requests , so it must have a fixed IP address . Therefore, in a network, you can only have one computer with one fixed IP address. The basic communication system is BOOTP with the UDP frame. When the machine starts up, it has no information about its network configuration, so there is nothing special the user needs to do to get the IP address .

In this type of case, transmission technique must be performed : That allows him to find and communicate with a DHCP server. To do this, the equipment must simply send special transmission packet , an example of this would be "Transmission in 255.255.255.255 with additional information such as type of request, connection ports and many other items. All this via a local network. "

Once DHCP receives transmission packet , it will respond to another transmission packet containing all the information requested by the customer . In this way, we can say that a single packet is more than enough so that the protocol is working correctly . But it should be mentioned that there are different types of DHCP packets, which can be issued either from server or servers to the client, or from the client to the servers .

These types of packages are:

• DHCPDISCOVER: Used to locate the servers DHCP availables.
• DHCPOFFER: This is the server's response to a packet DHCPDISCOVER, which contains the initial settings.
• DHCPREQUEST: for several customer requests.
• DHCPACK: This is the response from the server which contains the parameters and the client's IP address .
• DHCPNAK: This is the response from the server to indicate to the client that its lease has been executed, or when the customer is announced that one of the network configurations is wrong .
• DHCPDECLINE: The client is responsible for announcing to the server that the address is already used .
• DHCPRELEASE: In this case, the client releases his IP address .
• DHCPINFORM: The client decides to request the local parameters, he has already an IP address .

How does communication between client and server work in DHCP?

To better understand this, it is necessary to know how the communication between the client and the server works . Bearing in mind that this is where it happens automatic address assignment via dynamic host configuration protocol .

This whole process consists of four steps which we teach you below:

• In the first step, the DHCP client sends a DHCPDISCOVER packet with address 255.255.255.255 from address 0.0.0.0. With this broadcast or broadcast dite large , this is where the client establishes contact with all other members of the network , in order to locate DHCP servers availables. if there is only one server , the configuration will be very simple.
• All servers that listen to requests on the port 67 meet demand client with a DHCPOFFER packet , which contains a free IP address . THE MAC address and the client's subnet mask, and server ID and IP address.
• The next thing will be for the DHCP client of select a package and contact the corresponding server, in this case DHCPREQUEST . All other servers will also receive this message in order to be informed of the choice . In accordance with this notification, the customer request have to the server a confirmation of the data it has provided . This response is therefore also used to confirm the previously assigned parameters.
• Finally, the server takes care of confirm TCP / IP settings and this one the refers to the customer , this time via the DHCPACK packet. This package contains other data such as SMTP, POP3 or DNS servers . Le dhcp client decides to save locally all the data he has received and connects to the network. If the server does not rely on a address no longer available , proc that IP would be assigned to another client to answer with DHCPNAK .

Once all of this is done, the assigned address is stored in the server database with the client's MAC address . In this way, the configuration becomes permanent. Thus allowing the device always connect to the network with this address which was automatically assigned to it and which is no longer available to any other customer.

This means that the new customers will not be able to receive any addresses if all have already been assigned, even if some IP addresses are no longer used . All this caused a significant expansion of dynamic addresses and, in some cases, manual allocation via a DHCP server .

Advantages and disadvantages Is it practical to use these servers?

Considering everything mentioned above in the article, it is very important to know what are the advantages that this protocol offers and what are its respective disadvantages .

That is why below we are going to show you the pros and cons that can be achieved when using these types of servers:

advantage

• Have this dhcp protocol can offer certain advantages, one of which is that it allows save time in configuration , While the connection and disconnection of equipment is done automatically . It will make you save time when manually configuring IP addresses .
• Other benefits that you can get are the simplification of the network configuration. in this case, the user must simply connect the network cable or connect to the WiFi network, he will therefore not need knowledge to assign addresses. IP works by itself.

Disadvantages

• Enabling this protocol may also cause you inconvenience, especially in in matters of de security where the WIFI networks are most affected . Si the DHCP server is activated , an attacker can have an IP address as soon as he connects . Whereas if this protocol is not available , manual assignment will be required , and in the event that the IP range has been modified manually, le hacker or cybercriminal will have problems .
• Another drawback that can be reached when DHCP activation is that he will return difficult to identify of peripheral devices network and configuration of services that require static IP addresses, such as that the opening or closing ports .

Security on DHCP servers How reliable and secure are these servers?

One of the things that most worries about using this protocol is server security , especially since we consider that the security of networks WiFi is generally affected with them . In this way , DHCP has generally a weak point and it is that it can be easily handled. The client usually makes a discretionary call to all dhcp servers who can respond to his request, so that any attacker with the necessary knowledge can enter the network.

In a very simple way and impersonate one of them if you have had access to them. This is all called a unauthorized or corrupted DHCP server. The pirate will clearly try to go before with its response to the legitimate server, thus trying to succeed in order to send the manipulated parameters. Si the catwalks is not sent, un under - network is awarded à each customer or responds to all requests with the same IP address.

All this will allow the attacker to launch a denial of service attack. This will allow him to hack the router using fake gateway and DNS data, thus allowing him to be able to copy and hijack all data traffic . All this is done to obtain sensitive information such them mots de pass, postal addresses or bank and personal data.

Therefore, when using this protocol, it is necessary to implement all the necessary security measures that allow you to take advantage of all advantages offered by these servers , without worrying about some of these consequences. For this it is necessary to have absolute protection against any kind of attack, both external and internal , as well as a constant monitoring of all processes carried out on the network .

If you have any questions, please leave them in the comments, we will get back to you as soon as possible, and it will be a great help for more community members as well. Thank you!