DHCP dynamic host configuration protocol
DHCP stands
for dynamic host configuration protocol and it assigns IP address automatically
to the client, All devices on
a network has an IP address, which is like a phone number, which is used to
communicate with other devices on a network. DHCP is the application that
responsible for assigning addresses, making sure no two devices on the network
has the same address.
It is
necessary for all devices on a network to have an address (known as an IP
address), to be able to communicate with other devices on a network.
In-home
networks, the DHCP application is generally installed on your router, coming
reconfigured without making you set it up. In larger environments, network
administrators usually install it on a server. So how does it work
-When a DHCP the client is first switched on, it sends a broadcast packet on the network with a
DHCP request. This is picked up by a DHCP server, which allocates an IP address
to the PC, from one of the scopes (the pools of addresses) it has available.
Each DHCP scope is used for a different IP network segment. On networks with
routers that support DHCP, extra information is added to the request by the
router to tell the server which network the request came from. The DHCP server
uses this information to pick an address from the correct scope. The server
replies to the client, allocating it the IP address and settings required.
However, DHCP doesn’t allocate the address permanently. It tells the client
that it has “leased” the address to it for a specific time period, which you as an administrator can control. By default, DHCP is installed with a three-day lease
period. When the lease expires, the client can ask the server to renew the
lease. If the DHCP server doesn’t hear from the client beyond the expiry of the
lease period, it will put that address back in the pool ready to be re-used.
In order
for a new device to get an IP address when it connects to a network, it goes
through four stages:
- It broadcasts over the network
that it is looking for a DHCP server. This stage is called
Discovery.
- DHCP responds by offering it an
IP address. This stage is called Offer.
- The device responds to
the DHCP server and requests the offered address. This stage is
called Request.
- The DHCP server responds to the
device and acknowledges the devices new IP address. This stage is
called Acknowledge.
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