welcome to the Cisco netacad CCNA introduction to networks video series by
Jason Johnson this video is chapter eight subnetting IP networks the
material in this video covers the 6.0 version of the cisco netacad CCNA
introduction to networks course I want to thank you for watching my videos your
time is appreciated if you find the material helpful you can subscribe to my
channel and remember to click the notification button if you want to see
when I post new content if you have any questions you can leave a comment below
and if you watch to the end of the video I will have links to the next chapter
ok so chapter 8 subnetting IP networks and we're going to talk about why we
subnet networks and we're going to talking about submitting an ipv4 network
while we do that and explain how subnetting segments enables better
communication we're also going to look at a before we're gonna look at v6 we're
gonna look at addressing schemes we've got a whole bunch to cover here so three
sections here that we're gonna cover so let's move forward and let's talk about
first the network layer protocols now when we're talking about network
segmentation what do we mean by segmentation well we means we're
chopping that network up we're usually given an IP range or an IP number that
has a range of host IP addresses in it when we're given that and sometimes we
need to break that up because we need multiple LANs so with especially in the
v4 world the ipv4 world where we were given let's say that we were given a
slash 24 and we had X amount of hosts in there but now we need to have two
separate LANs to separate that out on our local area network so what we would
do is we would segment that out and we still do that so when we talk about
segmentation that we have broadcast domains and that's where each router
interface connects to a broadcast domain and broadcaster propagated within its
broadcast domain so if we look down here we've got a router here and this router
has a connection here and that's a broadcast domain broadcast domain or you
can think of that also as a LAN and then you have another one over here you have
number two and then you have number three over here so the problem with
large broadcast means is that slow network operations if
you have a lot what will happen if you have a lot of broadcast traffic so let's
just say that you have a hundred in endpoints and those will cause a lot of
traffic because if you remember back from previous chapters we have we have
computers we have the ones that they're sending ARP commands to each other
they're sending IMCP commands to each other and then just a traffic in general
is going to take up all of your bandwidth so what you want to do is plan
your broadcast domains or your local area network so you have smaller
segments or smaller broadcast domains so that you don't have all of that traffic
on there so slow device operations are because of a device must accept and
process each broadcast packet and so what we want to do is we want to put
domains into smaller areas or smaller groups when we do that so we do that by
subnetting and when we subnet the solution with subnetting was to reduce
the size of the network to create small broadcast domains or small LANs or local
area networks so because each broadcast domain connects to a different router
interface each domain needs its own network address space and the process of
breaking down an address range into a smaller address space is called
subnetting and you are gonna need to know how to subnet at some point in the
future you we will only subnet with ipv6 but for now you still need to know how
to subnet and I'm going to stop and and so you just need to know how to do it so
you need to learn how to do it I've got videos on how to do it there's lots of
other videos out on the internet on how to do it I've got what I think is an
easy way to do it but there's other ways to do it out there that I've heard some
of my students tell me that they found easy as well so network administrator's
can group devices into subnets that are determined by location organizational
unit or oh you you'll Co you from time to time or a device type now when they
break those up we have to give those segments or different what subnets and
you'll hear them call subnets that's what you'll hear them call you what you
won't hear broadcast domain usually usually you're not going to hear
broadcast domains or segments you're gonna hear the term subnets so with the
v4 subnet we have what we call Tett boundaries and if you remember if
we look down here at the bottom if you've been learning this material we
have four octet of ones and zeros which make up our IP address and our subnet
mask and so what we do is we subnet on the up what we call the octet boundary
it's also called a v4 classes we don't really use classes anymore the ABC and D
and E well they're still there but we really pretty much you want to learn
classless subnetting that's where it really work what did everybody is pretty
much doing now you may get some questions on classes on the ABCD and E
so you want to study that material it's in the netacad course or you can find it
out on the internet just just just search for classes IP range classes or
ipv4 classes and you'll find it what the classless subnet does is it uses address
bits to separate networks from hosts and allows for a lot more flexibility so an
example of that this would be a slash 25 and you might see an IP address that's
you know maybe 192 you know 192 I'll see if I can draw this out 1 9 2 1 6 8 10
dot 0 slash 25 or slash 24 or slash 26 this part right here is the Sider
addressing that slash is Sider addressing CIDR that's your cider
address your subnet mask is based upon that cider addressing i'm gonna go ahead
and say right here I'm not going to show you how to do subnetting in this video
that goes beyond the scope of this video I've got videos on how to do subnetting
on how to do a quick and easy way to look F chart to build a chart to be able
to say you can look at a slash twenty five real quick and say what is the
subnet mask now with the subnet mask in binary here see we're looking at the
subnet mask you on a slash 25 it's 255 255 255 dot 128 so 255 here is eight
ones 255 here is eight ones eight ones here and then the first IP address or
the first bit right here is 128 so we go one bit into the fourth octet and if you
remember from a previous video the way the network read
this is everything after that number of sub ones is the host so the host is over
here and the network is over here so everything to the left of that one the
one in to the left is the network and everything from this first zero and over
is your host so on this one that means we're going to be able to get two
subnets out of this and we're gonna be able to get a hundred and twenty six
hosts per subnet again don't let that confuse you on how we broke that up go
and watch my other video on how to do subnetting or subnetting made easy as I
think it's what my title I was on there and it will it will become a lot more
clear on how to get that information quickly on there so when we create two
subnets on there a subnet mask of slash 25 is applied so 192.168 10.0 is your
first network ID it creates two equal subnets each one with 126 hosts so we
have 126 host here and 126 host here and you may be saying to yourself why don't
we get 128 well 1 is used for the network ID and 1 is used for the
broadcast ID so we always we always break it up and then minus to 1 for the
network ID 1 for the broadcast ID other ways to do that is due to the N power 2
to the N power minus 2 is calculate your number of usable hosts so n is the
number of allocated to the network portion of the host that's that's one
way to do the subnetting some people can do it with the math and do it their head
I use a chart and if we're gonna create 4 subnets we go one more decimal place
or decimal place we go one more bit place and we get a slash 26 and so now
we get four equal subnets each with what 62 host not 64-62 because one is the one
is the network one is the broadcast and so that's the minus 2 which gives us 62
and again go watch my videos I've got links in the description below which
will show you how to do that so you might want to pause this video go watch
that other video and then come back to this one because it was or just watch it
afterwards it will make subnetting a whole lot easier for you
now when we create subnets with the slash 16 it goes the same way we get we
get create 65,535 host and then 18 gives us sixteen thousand three hundred eighty
two and then 22 gives us create 64 networks with a
thousand 22 see we went the other way see instead of going to the you know we
get hook we get host because we go to the left or to the right gives us more
host or less host depending up on the network IDC and I'm gonna go back here
see so depending on how we move our I depending on how we move our bit place
if we move it over here we get more hosts and if we move it this way we get
less hosts and it is back and forth and then depending on where the bit place is
is gonna be how many hosts and how many networks we have let me move forward
here so subnetting based on host requirements what you want to do is you
have to plan your networks out you want to put a little bit of consideration
into it and what you don't want to do is say I need to hope I need two subnets
and that's all I'm gonna ever need well you may need more than that down the
road so what you have to do is plan a little bit of future planning and that's
where you get with the business that you're working with or working working
for and you say you know what's your future growth plan to look like you know
what is it gonna be in a year to two years down the road what do you expect
it to grow to are you gonna add five new employees six months down the road do
you have a plan for that and if they do you want to make sure you plan for that
growth so two considerations when planning is that the number of host
addresses required for each network and the number of individual subnets needed
so for example if we have a router here let's say we have a router and we have a
subnet here in a subnet here and let's say that we have five hosts here and ten
hosts here and we have you know that goes out to the cloud we just you know
that's our cloud there that we go out to and so we know that we have we need 10
here and five here but let's say the company says we're gonna add another 10
here six months down the road so now we're gonna need 20 here and let's say
that they're gonna add another 10 here so we're gonna need 15 down the road and
let's say hey we're gonna be adding an accounting department in a year from now
when we expand and we want that to be separated so nobody can see it well
that's gonna add another subnet on here that you're gonna have to plan for so
make sure that you ask those questions ahead of time so that you can be able to
subnet that out because what you don't want to do is subnet this into two
and then have to come back in six months from now and resubmit it back out and
reapply all those IP addresses because it just it gets it gets a little bit
more messy that way and if you can do it clean from the beginning it makes it a
whole lot easier so subnet based on network requirements
administrators may be asked to submit an IP arranged to accommodate a specific
number of networks you want to think of a company with seven departments where
each department must have its own sub Network so you need seven subnets so the
number of hosts per subnet is secondary at that point because you need seven
departments but if you need seven departments with 50 hosts each you're
gonna need to make sure you plan for that so a network requirement example
would be assumed 22:48 298 slash 24 was given to you
seven subnets must be created and each department will have no more than 29
hosts each so you're gonna use a subnet mask of slash 27 that's gonna create a
networks and that's okay that you have an extra one but it's gonna create eight
subnets with 30 hosts each in each Network now what that's gonna do for you
is you're gonna run out of hosts really quickly so if they add they said they
only need 29 but if they add five more people in it to a subnet that's going to
say oh I'm out of host now and so I'm gonna have to figure something else so
you're gonna have to move and put them in that extra network that you had that
extra that extra subnet that you had or you're gonna have to figure something
out at that point so you just want to keep that into consideration when you
plan those post out are those subnets out now the traditional way of
submitting waste addresses because everything gets split up evenly so
subnets were based on classes it's not very flexible results in a lot of wasted
addresses so we went to vlsm and that's variable length subnet mask and you're
gonna hear the term vlsm you want to memorize that on what that is
so we vary the administrator or we vary the number of subnets or excuse me the
number of hosts in each subnet basic vlsm it's it's down here and then in
practice I'm gonna talk about it a little bit but again I've got a video
and it's called vlsm made easy and I walk through how to do vlsm I think what
I think is an easy way to do it so again that link will be I've got a playlist in
the description below and just check that playlist out and it's going
to have the videos on how to subnet on how to subnet in the fourth octet
you know advanced subnetting the basics of binary and also vlsm so when you do
vlsm for example and you have let's say that we have a router here and we have a
router here and we have a router here and we have a subnet here and a subnet
here like that well we're gonna need we're gonna need a subnet here so we're
gonna need one we're gonna need a subnet here for two and we're gonna need a
subnet here for three and we're gonna need a subnet here for four so you're
gonna need four subnets but I only need two IP addresses I only need one on this
lamp line and I only need one on this line
over here and in this subnet I only need one in two so you don't want to split
that up into four and say hey I've got all these posts now that are wasted in
here so what you do is you use vlsm to be able to say I'm only going to assign
two IP addresses here for hosts and then I'm gonna only assign two here and then
I'm gonna leave the rest of them for down here and down here and that's up
that's how blsm works and again check out my videos yes I'm doing I've giving
you a plug for my videos but I created them with the goal in mind of making
vlsm a lot easier for you alright so let's move to address schemes now when
we plan out network address planning it requires the decision of each subnet in
terms of size the number of hosts and how those addresses will be assigned
so you primary planning is you want to prevent duplication of addresses you
want to monitor security and performance and you want to provide and control
access so for example here we have three separate subnets here you have a student
land a faculty land on an admin land so they're gonna have separate IP
addressing so that they can have separate subnets and that provides some
security for you because you don't want students to be able to see the faculty
computers and you don't necessarily have the faculty seeing the admin computers
but you might want to be able to still pass information along back and forth
you might want to be able to email it also you would be able to pass those
services back and forth without actually seeing files on those actual endpoints
so different devices may also need to impact the addressing scheme for example
if you have printers network devices and gateways those those may need to have
separate subnetting and separate up addresses on there so if you have a
server or a printer let's say that we have a router here that those are all
connected to and then let's say we have a print server up here or a print server
and that print server is gonna be on separate network so that we can print to
that and they can be able to see that with security that's in place okay
so design considerations for ipv6 v6 is a little bit daunting to some when they
first see it if you're because it's such a large it's such large numbers and it's
hexadecimal it seems to be intimidating but it's really not if you just think
about it and take take it one step at a time and
just take it nice and easy you just have to understand how it's broken down in
hexadecimal so the v6 global unicast address is it
normally consists of a / 48 global routing prefix a 16-bit subnet ID and a
64-bit interface ID so 16-bit 7 a 19 a 64-bit down there
so the subnetting using the subnet ID the subnet ID provides plenty of subnets
and host support and one subnet and I think it's it's in the hits way above
it's it's just it's just a huge number you can go look it up so if you go and
look up the this is the number of hosts or this is the number of subnets that
allows a / 64 an assasin / 64 is breaking that hexadecimal ipv6 into so
it's only half in it and half of that 64 gives you 65,536 subnets not hosts
subnets and each one of those subnets gives you I forget what it is it's it's
it's a it's a number well above trillion I mean quadrillion or something like
that it's huge number you can go look it up you can you can go look up to the
number of IP addresses per 64 7f but it's just it's just off the charts large
number so the subnet allocation is is address waste is not a concern in v6 at
this point and v4 wasn't at the point they created it but it but quickly
become so but with such large addressing space I don't really think in my
lifetime I'm 50 years old I don't think in my lifetime in the next
50 years if I even if I live to be a hundred
I don't think we'll even get close to running out of IP v6 addresses
it's just it's such a large number that I just don't think we ever will so
administrators can concentrate on designing a logical scheme to address
the network and so here see we're using the first range there zero zero zero one
zero zero zero two four five and each one of those is going to have all kinds
of host addresses that you can do so everything can have an IP address and
that's where we come up with the term of internet of everything because
everything can be on the internet at some point so don't don't let it
intimidate you just take it just just research on the hexadecimal and research
the v6 and then understand that all right so we are bringing chapter eight
to a close we have looked at v4 addressing schemes we looked at the set
of requirements and how will you break down go check out my videos on IPR
subnetting go check it out on vlsm it'll make it a lot easier for you don't let
v6 become too daunting for you don't let it overwhelm you we briefly looked at v6
and how it breaks down you're gonna learn more about v6 in your material in
the netacad course so I hope this video was helpful for you if it was go down
and give me a thumbs up down below or leave me a comment I'd love to hear
comments from from those that watch my videos and I hope you have a great day