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

     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

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
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

ip: 10.0.11.12
sm: 255.0.0.0

nid => 10
hid: 0.11.12

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

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

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

SM = 255.255.255.0

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