What is Dynamic Host Configuration Protocol (DHCP)
Dynamic Host Configuration Protocol (DHCP) is nothing but a assigning a IP address automatically to a computer or device by using DHCP server.
Why Dynamic Host Configuration Protocol Is required?
Every computer on a network or device has to have an IP address for communication purpose. IP address is an unique identifier for computer or device on a network. In two ways that a computer can be assigned as IP address. It can be used by static IP or dynamic IP.
A static IP means assigning IP address manually for a computer or device. This was the original method done by beginning of networking. So each computer on a network had open the computer network configuration page and manually type an IP address, but addition to an IP addresses, subnet, default gateway and DNS server are to be entered.
For every computer is the same procedure. This could be a lot of work to do. If we want to deal with large network with lot of computers and IP address must be unique. While assigning if you assign the same IP address for twice it causes IP conflict then those computers will do not access to network.
A dynamic IP is where a computer gets an IP address automatically from a DHCP server.
A DHCP server automatically assign a computer as IP address addition to an IP address, it also assign subnet, default gateway and DNS server.
For example: we have the network properties open for network interface card on a Microsoft windows in a computer. Here it is set obtain an IP address automatically when you choose this option computer will broad cast as request IP address on the network.
The DHCP will assign IP address from its port and delivered it to computer. Once it assign we can verify all the different settings that DHCP server given to your computer and we can do this by opening command prompt on windows computer and type an IP configuration /all then press enter.
We can see DHCP enabled on this computer which mean getting its IP address from DHCP server, we can see IP address, subnet mask, default gateway and DNS server. All these settings are given by DHCP server. As we can tell dynamic IP address is the best because its automatic and manage network easier.
DHCP assigns IP address to computer on a network from its SCOPE. Scope is a range of IP address DHCP can handout. The range of IP address starts with 10.0.0.1 and ends with 10.0.0.100.
Computer on this network gets IP given from 100 IP address. These values can be customized by increasing or decreasing range. It all depends on network administrator wants to do.
A computer can obtain IP address from DHCP server. The server assigns the IP address as a lease. If computer does not actually on IP address it is actually a lease. A lease is the amount of time in IP address is assigned to a computer.
For example: lease could be one day. The lease is to make sure the DHCP server does not run out of IP address in its scope.
The DHCP scope only has a range of three IP addresses only we can give out only three IP addresses. Obviously it is not realistic no administrator will create scope this much smaller.
Let’s us go with three computers to network as their added DHCP server. DHCP server assigns their IP address actually and not as lease. DHCP is reached its limit giving out IP address all the IP address are currently being used.
Suppose if we removed one computer from the network what will happen let’s see. If the computer is removed the IP address is still been assigned to removed computer only. In the removed place if we add another new computer in the network the problem is computer is not able to access because the DHCP is run out from the IP address.
Even though the old computer is removed it still occupying the IP addresses. That IP address could not use for another computer.
This is why IP address are leased and are not given because IP address are leased this will tell DHCP server which IP address are still being used and which are not being used.
For example: IP addresses are leased. After certain period of time during the lease computer will send a signal to DHCP server asking server to remove its lease of IP address. In other words informing DHCP server it is still present on network and its IP address is still being used.
If computer is removed from the network that computer is not going to ask DHCP server for renewal if doesn’t ask for renewal the lease will expire and IP address will go back to IP address port. Now the IP address is used for another computer. That’s why IP address are leased.
If we want computer or device on your network to have specific IP address all time. Other words never want to change IP address every time. We can create reservation on DHCP server.
A reservation ensures that a specific computer or device identified by MAC address where always given the same IP address that computer or device request IP address from DHCP server.
For example: DHCP server if create reservation for my computer DHCP server recognize my MAC address always gives certain specific IP address 10.0.0.1.
Reservation is not typically given to all computers. They are typically given to special devices or computer. Such as network, printer, server, etc., because devices like this should be given to same IP address constantly.
DHCP is a service that runs on a server, such as Microsoft server or Linux server. It’s also run services that run on routers. Routers are a given to buildings, small office etc.