Networking contd

Network

• Network is used to connect devices
• Each device in a network gets an unique id which is referred as ip address.
  
• Ip address = network id + host id
• There are two schemes of ip addresses
  • ipv4:
  • ipv6
    
• ipv4 is a 32 bit number divided into 4 equal parts and each part is referred as octet

X.X.X.X
range: 0.0.0.0 to 255.255.255.255

• Lets find network id and host id.

     1   2  3  4
ip: 192.168.0.105
sm: 255.255.255.0
-------------------

• Network Id: What octets have 255’s in subnet mask => 1, 2, 3. The equivalent in ip

192.168.0

• Host Id: What octects have 0’s in subnet mask => 4

105

• network id is constant/fixed for all devices in a network and hid is unique for every devices
• Summary

ip: 192.168.0.105
sm: 255.255.255.0
-------------------
nid: 192.168.0
hid: 105

• Size of network is number of hosts which you can connect to a network. the host id is deciding factor

nework size = 2^ (number of host id bits) - 2
hid = 1 octet => 8 bits => 2^8 - 2 = 256 -2 = 254

• references
  • 2 power table
  • binary to decimal converter
  • decimal to binary convertor
• consider the following example and find host id, network id and size of the network

ip:  172.16.10.17
sm:  255.255.0.0

nid: 172.16
hid: 10.17

size = 2^16 -2 = 65536-2 = 65534

• consider the following example

ip: 10.0.11.12
sm: 255.0.0.0

nid => 10
hid: 0.11.12

size => 2^24 - 2 = 16777216 - 2 = 16777214

• Lets find the subnet mask based on our size needs
• I need a network to connect 150 devices

2 ^ n - 2 = Size
  n => 8,16,24

2^n ~= Size
2^n  = 150
 n = 8

SM = 255.255.255.0

• I need a netowrk to connect 270 devices

2^n ~= 270

n = 16

SM = 255.255.0.0

• Since this scheme has a chance of creating networks which are way larger than needs, the alternative apporach is to look at SM as bits rather than octets
• That means network id is number of bits where you will be having continuous 1’s and host id bits where you be having continous 0’s
• I want a network of 280 devices

2^n-2 = size

2^n - 2 ~= 280
n = 9 (number of host id bits)
total bits = 32
network id bits = 32 - 9 = 23

SM: 1111111.1111111.1111110.00000000