Dynamic Host Configuration Protocol ( DHCP )

  • Every computer in the network has to have an .
  • There are two ways in which IP Addresses are assigned to the computers.

Static IP

  • In this method, the is to the by the .
  • This was the original method that was done at the beginning of the networking.
  • To do this, every time you have to open the computer’s network configuration page and manually type in the along with the , , and .
  • So each time when you want to add a computer to the network or device to the network you have to do it and it might turn tricky while dealing with a large network that has a lot of computers.
  • The major problem here is ( ie ) having the , and configuring them manually will likely lead to errors.
  • Even on small networks manually assigning IP addresses can be confusing, particularly with mobile devices that require IP addresses on a non-permanent basis.
  • Also, most users aren’t technically proficient enough to locate the IP address information on a computer and assign it.
  • Automating this process makes life easier for users and the network administrator and this is where we use

Dynamic IP or DHCP

  • In this method, and other pertinent configuration parameters are assigned to the computer by the
  • The computer would a request for an IP Address on the network and then the will assign an IP Address from its and deliver it to the computer.
  • The has a of IP Addresses that can be used to assign to the computers.
  • Theassigns IP Addresses as a so that the computer doesn’t actually the IP Address.
  • is the amount of an IP Address is assigned to a computer.
  • The lease is to make sure that the doesn’t run out of IP Addresses.
  • If this method of the lease is not used then if the computer which is assigned the IP Address is removed, it takes the IP Address that has been given to it.
  • So in this case, if some other computer gets added to the network as well as the DHCP server has run out of IP addresses, it won’t be able to access the network because the DHCP server has run out of IP addresses.
  • So even though the computer has been removed it's still occupying an IP address that could be used for another computer.
  • This is why IP addresses are leased and are not given because if the IP Addresses are leased then this will tell the DHCP server which IP Addresses are still being used and which ones are not being used.
  • If the lease expires, the IP address will go back to the IP address pool.
  • So now the IP address can be used for another computer.
  • will ensure that a identified by its , will always be given the when that computer or device requests an IP address from the DHCP server.

Components of DHCP

  • A networked device running the DCHP service that holds IP addresses and related configuration information. This is most typically a server or a router but could be anything that acts as a host, such as an SD-WAN appliance.
  • The endpoint that receives configuration information from a DHCP server. This can be a computer, mobile device, IoT endpoint or anything else that requires connectivity to the network. Most are configured to receive DHCP information by default.
  • The range of addresses that are available to DHCP clients. Addresses are typically handed out sequentially from lowest to highest.
  • IP networks can be partitioned into segments known as subnets. Subnets help keep networks manageable.
  • The length of time for which a DHCP client holds the IP address information. When a lease expires, the client must renew it.
  • A router or host that listens for client messages being broadcast on that network and then forwards them to a configured server. The server then sends responses back to the relay agent that passes them along to the client. This can be used to centralize DHCP servers instead of having a server on each subnet.



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S Abhishek

Data Engineer Intern @Rolls-Royce | Computer Science Undergraduate | Amrita Vishwa Vidyapeetham | Former Member of security research & CTF team — @teambi0s.