CCAN Full Arabic Course : Session 7 Layer 3 Internet Layer ( IPV4 Header )

before we start let's take 2 examples on Subnetting first

Example 1 : For the given Major network : 199.20.30.0/24

we want to divide it using subnet mask 255.255.255,128

find : 1-Subnet mask in slash form

          2-number of subnets

          3-number of IPs/Subnet

          4-Number of hosts/subnet

solution : 199.20.30.0 is class C IP address (Network part is 24 bits , Host part is 8 bits )

and mask 255.255.255.128 is 11111111.11111111.11111111.10000000  mean /25

mean we borrow 1 bit from Host part 

SN=1 ....Number of subnets = 2^SN = 2^1 = 2

H=7 ......Number of IPs = 2^H = 2^7 = 128

Number of Hosts = 2^H-2 = 128-2 = 126

Example 2 : For the given Major network : 173.15.0.0/16

we want to divide it using subnet mask 255.255.252.0

find : 1-Subnet mask in slash form

          2-number of subnets

          3-number of IPs/Subnet

          4-Number of hosts/subnet

solution : 173.15.0.0 is class B IP address (Network part is 16 bits , Host part is 16 bits )

and mask 255.255.252.0 is 11111111.11111111.11111100.00000000  mean /22

mean we borrow 6 bit from Host part 

SN=6 ....Number of subnets = 2^SN = 2^6 =64

H=10 ......Number of IPs = 2^H = 2^0 = 1024

Number of Hosts = 2^H-2 = 1024-2 = 1022

Note : there is old subnetting standard use in some countries and old operating system 

   the standard is : While subnetting don't use first and last subnet and leave them for future use 

بمعنى انه يتم ترك اول واخر subnet لل future use اى لو بعمل subnetting اركز انى مخليش عدد ال Subnets=2 لانى مش هعرف استخدمهم وبالتالى 25/ لو كانت Class C لا يمكن استخدامها فى هذا ال Standard 

 

Internet Layer Protocol :-

IPV4 Header 

هنعرف شكل ال Header اللى بيتم اضافته على ال Segment لتتحول فالنهايه الى Packet 

ال data القادمه من Layer 4 تسمى Segment 

ال data القادمه من Layer 3 تسمى Packet

ال data القادمه من Layer 2 تسمى Frame