DHCP (Dynamic Host Configuration Protocol) explained.

DHCP, four letters that network administrators love. Would you like to know why?

What is DHCP? 

The Dynamic Host Configuration Protocol (DHCP) is a helpful solution for management, very used on TCP/IP networks. It provides automatically IP addresses and all the necessary network configurations (DNS server, default gateway, etc.) to connected devices to communicate. 

The magic word here is “automatically”. Usually, such tasks are executed manually by network administrators. If they manage a small network, it can be ok. But talking about big networks to be in charge of that can really be overwhelming. 

Dynamic Host Configuration Protocol works on a client-server model. Clients must have DHCP to communicate with a DHCP server properly. 

How does DHCP work?

If we consider just the assignment of IP addresses, let’s say that every device that connects to a network requires a unique IP address. The same IP address can’t work for two or more devices. If, by mistake, one IP address is given to two different devices, the connection won’t work, or perhaps, only one will manage to get it but not the other.

Once an IP address is given and the connection works, there is still constant monitoring over it, with different management’s objectives. If it expires but the device wants to keep connected, the IP address must be renewed. It’s also important to check when the IP address is not in use anymore because more devices connected ask for one, and administrators can’t run out of resources (IP addresses).

When you have DHCP, all these tasks can be configured in the most convenient way for you, and then they will happen automatically without the need for human supervision. 

What is the DORA process?

Dynamic Host Configuration Protocol works through a four-step process. Four messages are exchanged between a client and a DHCP server. 

D”, DHCP Discover message. A connected device needs an IP address. To request it, the first message it sends to the network is to discover a DHCP server that can provide it.

O”, DHCP Offer message. Once the Dynamic Host Configuration Protocol server receives the discover message from a client, it will respond with the requested IP address. It will offer this resource to the device.

R”, DHCP Request message. The device receives the IP address, and it will send a request message where basically it will say something like: “I’m ok with the resource (IP address), assign it to me”.

A”, DHCP Acknowledgement message. The DHCP server receives the device’s message accepting the IP address. Then, it will supply the IP address and all the necessary data and configurations for using it (DNS server, subnet mask…). It will register information related to the device, like:

  • The IP address assigned. Number sequence.
  • The expiration date of the IP address. Remember, this resource can be used for a specific period of time. When the use time finishes, it gets back to the IP pool, and it will be supplied to a different device. 
  • Media access control address (MAC address), the unique identifier given to a network interface controller (NIC) to use as a network address for communications that take place in a specific part of that network.

Benefits of using DHCP.

  • Managing IP addresses for your network will be easier and more efficient. All tasks related to them can happen without you checking them one by one. 
  • Human mistakes while managing IP addresses will be fewer. 
  • Configurations, changes, and upgrades related to those complex serial numbers will be managed accurately by DHCP. 

Conclusion.

The possibility of making daily, repetitive tasks happen automatically is really attractive. DHCP is a smart choice. Try and experience its efficiency directly. Your network’s productivity will be truly improved.  

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