Networking Basics: Part 2

DHCP (Dynamic Host Configuration Protocol)

The DHCP is responsible for assigning IP addresses to hosts on the network. DHCP is imperative to the running of the network, if DHCP was not used then IP world be allocated manually, this would lead to conflict occurring as two hosts would have the same IP addresses. It is a client-server protocol. For computers to work on the network they each need a unique IP address. It can be explained clearly in steps:

  • Step 1 – The DHCP client, which is the computer, broadcasts a message to all other devices on the network, this message is looking for the DHCP server. All other devices that receive the message that are not the DHCP server ignore the message.
  • Step 2 – DHCP receives the message and then broadcasts a message containing an unused IP address. If more then one IP address offer is given then the host will choose the first one it receives. The other hosts that already have a local IP address ignore this message.
  • Step 3 – The DHCP client, host, sends a message to the DHCP server saying that the host accepts the give IP address.
  • Step 4 – The DHCP sends the IP address to the host along with the subnet mask, default gateway and DNS server. The DHCP server gives the IP address to the host for a leased time, it also keeps a record of all the IP addresses and their leased times.
  • Step 5 – After the leased time is expired the same IP address is renewed. But if the host doesn’t respond then the IP address will return to the DHCP server, this prevents IP addresses from being wasted on old computers that are not going to be used any more.
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