Understanding IPv4 Addresses: Structure, Notations, and Validity

in today's lecture let's see the part one of ipv4 addresses we will start the session with the outcomes

in today's session we have three outcomes let's see what are they upon the completion of the session the

learner will be able to outcome number one we will understand the ipv4 address in detail outcome number two we will see

the notations of ipv4 address and the last outcome we will know the valid and invalid ip addresses with the help of an

activity let's start the session with what is ipv4 address ipv4 address or simply ip address stands

for internet protocol address internet protocol is a very important protocol in the network layer we know network layer

is the layer 3 in the osa reference model what are the things that will be there in the network layer the network

layer will create a packet this packet will definitely have the source ip address and the destination ip address

so any node in the network is identified with the help of mac address and ip addresses so ip addresses are logical

addresses that are dealt in the network layer so a packet will definitely contain the source ip address and the

destination ip address an ipv4 address is a 32-bit address that uniquely and universally defines the connection of a

device for example a computer or a router to the internet so in the internet any node is

identified with the help of this ip address only suppose if i am requesting for a packet from google.com so my node

is identified with the help of ip address and mac address and the application is identified with the help

of port numbers so from my device it has to reach google's computer so throughout the network that is in the internet it

needs ip addresses and what about the size an ipv4 address is of 32 bits long 32 bits means it is

of 4 bytes so any ipv4 address is of 32 bits long we also have another version of ip address which is ipv6 address

which is of 128 bits long we will be talking about ipv6 address in the coming lectures and two devices on the internet

can never have the same address at the same time this is a very important point so two devices cannot have the same

address at the same time if it is a local area network we will never resign the same ip address to two different

devices we know ip conflict will happen and communication will not happen but we can't expect that in the internet

say i have a computer and that computer is connected with the internet and i am giving the ip address as 10.10.10.1

can i expect nobody in the world should use 10.10.10.1 for their computers

i can't expect because everyone has their privilege to use their own private ip addresses in the upcoming lectures i

will explain what are private ip addresses and what are public ip addresses in the internet we need

uniqueness in terms of ip address i can't expect everyone in the world to use unique ip addresses but how it is

handle say i am requesting a google page from my computer which is 10.10.10.1

and many people in the world may use the same ip address which is 10.10.10.1 if i request the google page only my

computer is receiving that google response nobody in the world is getting that how this is handled

and that's the power of nat technology network address translation this nat converts the private ib addresses to

public ip addresses where these public ip addresses are unique throughout the world

and what about the address space of ipv4 the address space of ipv4 is to part 32 why 2.32 because an ip address is of 32

bits long so 2.32 means we will get more than 4 billion ip addresses we can have more than 4 billion ipv4 addresses but

in reality we have billions and billions of devices can we assign unique ip address that is unique ipv4 address to

all the devices how can we handle billions and billions of devices with just 4 billion ipv4

addresses and the answer for this is also the nat technology which is network address

translation we will be seeing this network address translation in the coming lectures

we will see the notations of ip address basically there are two prevalent notations to show an ip address number

one the binary notation and number two the dotted decimal notation and this is the example of binary notation we have

already seen that ipv4 addresses they are of 32 bits long so we will have 32 bits in the ip address and we have four

octets and how many bytes four bytes this is byte one by two by three and byte four each byte is of eight bits so

we can say there are four octets in our ip address we can represent the ip address in the other format which is the

dot decimal notation so where we have four decimal values which is separated by dots so 117.149.1

is an example.decimal notation so this is the binary representation and it's

equivalent.decimal representation and what about the range of each octet we know this is in the decimal we will see

it in binary if all bits are 0 that is the starting of ipv4 address and if all bits are 1 that's the ending of the ipv4

address so any octet if we take the notation of an ip address which can be a dot b dot c dot d

this will have only four octets this is an octet b is an octet c is an octet and d is also an octet so a b c d all are

octets and an ipv4 address will have exactly four octet and the range is any octet will be greater than or equal to

zero and obviously it will be less than or equal to 255 why it is zero if all bits in an octet is zero then in the

decimal it will be 0 if all 8 bits are 1 in an octet then the maximum value is 255 so any octet will take the value

between 0 and 255 so 0.0.0.0 is the starting of the ipv4 address and all once in binary which is

255.255.255.255 is the last ipv4 address we have various classes of ip address

and we have private ip addresses public ip addresses loopback addresses we will be covering all these topics in the

coming lectures we will see the valid ip addresses ip addresses shown are valid ip

addresses why we are saying they are valid because they have exactly four doctors

and the values in all the octets is between 0 and 255 so this contains private ip addresses and public ip

addresses i am not going to touch about the private and public ip addresses in this lecture for time being we will know

valid ip addresses means it should have only four doctors and in every octave the value should be between 0 and 255 we

will see some invalid ip addresses so these are invalid ip addresses why the first example it seems like a valid ip

address because every octet is between 0 and 255 but when we look cleanly we can see there are five octets one two three

four five a valid ipv4 address will have only four octaves in the second example we have only four octets one

two three and four and the values are also between 0 and 255 in every octet but still it is invalid why because this

65 is prefixed with zero so prefix 0 is not permitted in ipv4 address so the valid ip address will be 10.65.34.56

and not as 0.65 and the last example seems to be valid but when we look at the third octet which is 256 a valid

ipv4 address will be between 0 and 255 in every octa where 256 is bigger than 255 so we can't get 256 with the help of

8 bits right and that's why they are invalid now there is an interesting activity for you this activity will help

us to find out valid and invalid ip addresses and more precisely we will be able to find out the invalid ip

addresses with the reason the activity is spot the error if any in the following ipv4 addresses and the

ipv4 addresses are given and we will spot the error pause this video for a while and think of the answer

i hope you are done let's check the answer in the first one we can see there are only four octaves but there is a

prefix zero so the answer is there must be no leading zeros zero four five is not permitted simply 45 is accepted and

what about the second example one two three four five there are five octets any ipv4 address will have only four

octets and what about the third example one two three four we have four octaves but we can notice the third octet is

bigger than 255. every octet in an ipv4 address must be between 0 and 255. so this is invalid because the range of

each octet is between 0 and 255 and the last one is a combination of binary and decimal so a mixture of

binary and dotted decimal notation is not allowed i hope you enjoyed this activity

we understood the ipv4 addresses we saw the notations of ipv4 errors number one the binary notation and number two the

dot decimal notation and we also come to know the valid and invalid ip addresses with the help of an activity i hope you

guys enjoyed the lecture and thank you for watching [Applause]

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