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Hey everyone and welcome back. Now in the previous nugget we had discussed the very basics around

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the dynamic host configuration protocol. Now we learned that we would have to invoke a DHCP server

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in order to hand out the IP addressing to our client network. Now in this nugget right here

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that is exactly what we're going to be focusing on. We're going to be focusing on the DHCP server

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component of this interaction. So with that said how about we dive in and begin the configuration

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then. Now the very first thing that we want to do is we want to install a DHCP server. So what I'm

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going to see here is sudo apt and I'm going to say isc-dhcp and then hyphen server. If I hit enter

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in fact I should actually say apt install getting ahead of myself as per usual so that looks a

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little bit better let's hit enter I'll type in my password okay perfect I'll say why hit enter

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and the installation should complete. Great so what I will do is I'll clear the screen.

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Now the first thing to note is that when we install this server package there is going to be a DHCP

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configuration file. Now depending on the distribution that you have this may be in a different location

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you may find it in the etsy directory and directly within that you may have a file called DHCP-d

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for the DHCP daemon and this will be .conf. Conversely you might actually have within the

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etsy directory another directory called DHCP and then within that directory have a DHCP-d .conf.

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So really depending on the distribution you may or may not have this sub directory here. Now

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another important configuration file we want to know is going to be within the etsy directory

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and then within here the default directory and within that directory we should have a file called

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isc dhcp-server. Both of these configuration files are going to be important for us so let's go and

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check these out then the first one we will check out is going to be the dhcpd .conf file so let's

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go there then. Now on my distribution I happen to be in the configuration file resides within

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and within the sub directory DHCP within here as we can see we have this dhcpd .conf if I happen

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to open this one up and I hit enter now you will recall that when we discussed DHCP in the very

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first nugget we learned that DHCP can also handle DNS based information so this is what we're going

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to be able to specify right here so we can see here the option domain name in this case we have

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example.org I can maybe change this to let's just say the domain name was CBTNuggets example.com

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whatever it may be and then I can specify the option domain name servers in this case here I

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could just hand out let's maybe say google's public DNS which would be 8.8.8.8 and then we can specify

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a default lease time now we can see here that this is 600 that is 600 seconds this ultimately

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translates to 10 minutes now we also have a max lease time this is 7200 seconds i.e. two hours

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and if I scroll on down we have this option here ddns update style so with respect to DHCP we have

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the option for our DHCP servers to participate in updating our DNS zone file records in the case

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here this option is specifying the value none i.e. we do not want to attempt to do any type of

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updating for our DNS servers now if we scroll on down once again we come here to our subnet

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directive we see this right here now this happens to be all commented out so it's not actually taking

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effect but we can create our own range that will take effect so what I will do here is I will use

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keyword subnet and then I will specify a particular subnet so let's maybe say that we're going to have

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a DHCP server that is going to hand out IP addresses within the 10.1.1.0 range and we'll have the subnet

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mask of slash 24 which is 255 255 255 0 and then we can do our curly brace so what we're specifying

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here is the network which is going to be 10.1.1.0 slash 24 and then within here we want to specify

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the actual range of a loud host that we can give out so I could say 10.1.1 and then let's maybe start

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from IP address 20 and we will go to 10.1.1 let's maybe say 100 so that is all we're going to be

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giving out the very first client that requests an IP address they will get 10.1.1.20 the next one

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will get 21 the next 22 all the way up to 100 in which case after that our IP address range will be

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exhausted so what we want to do here is to have a semi colon and now what I'm going to say here is

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option or routers and what this is going to do it's going to allow us to specify a default gateway

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so let's imagine that the default gateway happened to be the very first address within this range

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so that would be 10.1.1.1 and then I can do my semi colon and then my curly brace and what we've

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done here is create a simple DHCP pool like I say this is the network we are targeting anyone

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who wants an address can get the IP addresses from 20 all the way up to 100 and when they make

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that request they will also be given their default gateway information of the very first

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address within that network 10.1.1.1 now you can actually specify more information right here we

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could maybe say you know the default lease time we could have a very specific lease time for this

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particular range so we could maybe say 2000 seconds and the max lease time could be maybe say 5000

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seconds and if we wanted to have different domain name configurations for this particular pool we

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could say option domain name and let's just say the domain here for this one was ipv0.org in fact

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I'm forgetting my semi colon here just notice that and in this case here we will say option

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domain name hyphen servers and we will give this a different ip address of 8.8.4.4 and

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semi colon now there definitely are more configurations that we can change and configure

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within this particular file we can do things like static host configuration but for now

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that is all we're going to focus on and in fact before I actually even do anything I've just noticed

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a very big error on my part before we actually specify the range of ip addresses i.e. this range

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right here I actually need to prepend this with the keyword range so this is very very important

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just as well I caught that there just remember to do that don't make the same mistake as me

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otherwise the configuration will absolutely not work so with that said this should be a valid

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subnet configuration and so what I'm going to do is I'll save this and I will exit out we can see we

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already have an interface here with an ip address in this case so I have added another ethernet

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interface to my device enp0 s8 if I wanted to listen on this interface for devices requesting

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dhcp information I could actually specify that I want to listen on this interface and I would do

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so within the etsy in fact the better say sudo nano the etsy directory default isc dhcp server

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now within here down at our interfaces I would just specify the name of the interface in which I

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want to listen so that would be enp0 s8 and conversely if I wanted to have a dhcp version 6

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server that is handing out ipv6 addressing then I could also specify that too but in this case here

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I will just leave it at v4 so if I save this so if I just happen to open the file once more for

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our main configuration there we go remember our subnet range is in the 10110 network so what I could

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do is I could say sudo ip adder and I could add the network of 1011 and give my interface an address

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of maybe say 3 slash 24 and I'll put this on dev enp0 s8 and if I do an ip adder we can see this

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interface here has an ip address within this particular range so what could now happen is if

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I draw my little server here this is my ubuntu machine which is now a dhcp server I have my

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interface here which is enp0 s3 this ultimately connects to the internet and I now have another

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interface here which is enp0 s8 and this has got the ip address of 10113 so now if anyone

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happened to be connected on the same network here let's imagine we had a switch and a whole

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bunch of different client computers all connected if on that same network segment someone sends out

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that broadcast address trying to discover a server we could then reply with an offer within our

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particular pool and that client could either accept or refuse that offer and that really is

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the basics of what we want to understand for the purposes of our dhcp configurations we have that

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main configuration file whereby we can specify our leases we can specify our dns server configuration

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we want to hand out the default gateway configuration as well as the network we are serving and the

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valid range of addresses we want to serve out and we also have that additional configuration file

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which specifies which interface we want to be listening on for incoming dhcp requests in this

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case here we're specifying enp0 s8 but notice here that this is all revolving around devices

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within the same network here so all these devices here are connected on the same network segment

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what would happen then if we happen to have a server on a completely separate segments from

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a potential client that would want to use its dhcp services well the reality is we do have a solution

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for that that's called a dhcp really and that is what we're going to be talking about in the very

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next nuggets i hope this has been informative for you and i'd like to thank you for viewing