DHCP Explained – Dynamic Host Configuration Protocol

DHCP Explained – Dynamic Host Configuration Protocol


hello everyone in this video we’re going to talk about DHCP or dynamic host configuration protocol now every computer or device on a network has to have an IP address for communication purposes an IP address is an identifier for a computer or device on a network and there are two ways that a computer can be assigned an IP address they could be done by using a static IP or a dynamic IP now a static IP is where a user assigns a computer or device with an IP address manually now this was the original method that was done in the beginning of networking so for each computer on a network you had to open up the computer’s network configuration page and manually type in an IP address but in addition to an IP address you also have to type in a subnet mask default gateway and a DNS server and anytime that you wanted to add another computer or device to the network you had to do the same thing so as you might have guessed this could be a lot of work especially if you are dealing with a large network that has a lot of computers and you also have to make sure that all the IP addresses are unique because if you assign the same IP address twice it would cause an IP conflict and would cause those computers to not have access to the network but there is a better and easier way to assign a computer an IP address and this is called a dynamic IP a dynamic IP is where a computer gets an IP address automatically from a DHCP server a dhcp server automatically assigns a computer with an IP address and in addition to an IP address it can also assign a subnet mask default gateway and a dns server so as an example here we have a network connection properties window open for the network interface card on a Microsoft Windows computer and as you can see here this computer is set to obtain an IP address automatically so when you choose this option the computer would broadcast a request for an IP address on the network then the DHCP server will assign an IP address from its pool and deliver it to the computer and then once that’s done you can verify all the different settings that the DHCP server has given your computer and you can do this by opening up a command prompt on a Windows computer and then type in ipconfig space forward slash all and then press Enter so as you can see here the DHCP is enabled on this computer which means that it’s getting its IP address from a DHCP server and then you can see the IP address here along with the subnet mask default gateway and DNS server so all of these settings were given by the DHCP server so as you can tell dynamic IP addressing is the best choice because it’s automatic and it makes managing a network a lot easier now a DHCP server assigns IP addresses to computers on a network from its scope and a scope is a range of IP addresses that a DHCP server can hand out so as an example here we see a scope of IP addresses on this server so as you can see the range starts with this IP address and ends with this IP address so computers on this network will get an IP address from this range of IP addresses so this scope can give out 100 IP addresses now these values can be customized to either increasing or decreasing the range it all depends on what the network administrator wants to do so it is customizable now when computers obtain an IP address from a DHCP server the server assigns the IP address as a lease so the computer doesn’t actually own the IP address it’s actually a lease and a lease is the amount of time an IP address is assigned to a computer for example the lease could be for one day now the reason for the lease is to help make sure that the DHCP server does not run out of IP addresses in its scope so as a demonstration let’s just say that this DHCP scope only has a range of three I pee addresses so it can only give out three IP addresses now obviously this is not very realistic because no network administrator is going to create a scope this small but for this demonstration let’s just use this as an example so let’s go ahead and add three computers to this network and as they are added the DHCP server is going to assign them an IP address so in this example let’s just say that the IP addresses are actually given to the computers and are not least so the DHCP has reached its limit on giving out IP addresses all of its IP addresses are currently being used but what happens if one of these computers is removed from the network so if a computer is removed it takes the IP address that it has been given with it so let’s say another computer gets added to the network but the problem is the computer won’t be able to access the network because the DHCP server has run out of IP addresses so even though this computer here has been removed it’s still occupying an IP address that could be used for another computer so 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 so in this example the IP addresses are leased so after a certain period of time during the lease the computers will send a signal to the DHCP server asking a server to renew its lease of the IP address so in other words it’s informing the DHCP server that it’s still present on the network and its IP address is still being used so if a computer is removed from the network that computer is not going to be able to ask the DHCP server for a renewal and if it doesn’t ask for a renewal then the lease will expire and then the IP address will go back to the IP address pool so now the IP address can be used for another computer and this is why IP addresses are leased now if you wanted a computer or device on your network to have a specific IP address all the time in other words you never want that IP address to change or you can create a reservation on the DHCP server a reservation ensures that a specific computer or device identified by its MAC address will always be given the same IP address when that computer or device requests an IP address from the DHCP server so for example on this DHCP server if I create a reservation for my computer the DHCP server will recognize my MAC address and will always give me this specific IP address now reservations are not typically given to regular computers they are typically given to special devices or computers such as Network printers servers routers etc because devices like these should be given the same IP address constantly now one final thing to note about DHCP is that DHCP is a service that runs on a server for example this could be a Microsoft server or a Linux server but it’s also a service that runs on many routers also whether the router is a business router or a small office/home office router these routers will have a DHCP service built into them you

11 Comments

  • andy joe

    September 28, 2019

    wow, wow, wow,,.,.,.,.,.,.,.,.,.,.,.,.,.,.
    I'm amazed at the way you make the videos & explain………….
    even a kindergarten child can understand it clearly……………
    AMAAAAZING!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    Reply
  • zaib un nisa

    September 29, 2019

    Sir i hv a question that dhcp assign an ip to any pc.but it does not allow to do it by pc.what are the reasons behind that???

    Reply
  • Gary Sanderson

    September 29, 2019

    А по русски можно?

    Reply
  • Navid Rigi Ebrahimi

    September 30, 2019

    you're the best

    Reply
  • Dennis Njoroge

    October 3, 2019

    Give us Cisco Videos Please.

    Reply
  • John Broxon

    October 3, 2019

    Hey – how do you get these animated icons for the video? How to get these into a regular powerpoint?

    Reply
  • Atta Asare Eric

    October 3, 2019

    you are too much boss

    Reply
  • pippo spano

    October 4, 2019

    the DHCP server blinks like a stereo set

    Reply
  • Mohamed Khan

    October 4, 2019

    Really easy to understand, thanks for a great content

    Reply
  • Priya

    October 5, 2019

    Awesome tutorial I understood so easily

    Reply
  • Vedang Tikam

    October 9, 2019

    Why burn the computer and router at the end lol. Thank you for the amazing videos just found your channel. Subscribed ☑️☑️

    Reply
  • Anonymous

    October 11, 2019

    very informative thank you.

    Reply

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