Importance of Virtual/Software defined Networks

• When we use cloud to access the applications we need to figure out how to use virtual networks for that we need to have some basics of networking
  

Networking Basics

• Ip address is used to uniquely identify a device on the network.
• Let me find the ip of my laptop. On windows ipconfig or linux ifconfig or ip addr
  
• Networking principle:
• A device can connect directly to other device in the same network.
• Whenever network packets need to travel to the different network they use router.
• Default Gateway in the ipconfig is the ip address for the router
• Lets understand IPv4 => x.x.x.x where each x is an octet i.e. it has 8 bits. The range of ip address is from 0.0.0.0 to 255.255.255.255
• Ip address is combination of network id and host id

ip => network id  + host id

• Find the network id and host id

ip: 192.168.0.10
sm: 255.255.0.0
octets with 255: 192.168 => network id
octets with 0: 0.10 => host id
host id => 2 octets => 16 bits => 2^16 - 2 = 65536-2 => 65534
if the host id has all zero's => network id
if the host id has all one's => broadcast id

• Example 2

ip: 10.11.12.13
sm: 255.255.255.0
nid: 10.11.12
hid: 13
size => 2^8-2 => 254

• I want to create a network to connect 60000 devices

2^n ~= 60000
n = 16 => 2 octets
sm => 255.255.0.0