Subnet Mask

To identify which portion is the address and which portion is the host

For example,

1. subnet 255.255.0.0 can be present as:
   • 11111111.11111111.00000000.00000000 in binary. The 1111.. part is the address part where as the 000... are the host part.
   • This can also be called /16 since we have 16 1.
   • So when there is an ip in here, for example 192.168.2.1, we know that the 192.168 cannot be changed (Since the subnet is 255), what can be changes is the 2 and 1
     • Which can result to 2^16 available hosts = 65356 - 2 = 65354 (we cannot use Broadcast address and Network address)

• Similarly, 255.255.255.0 can be present as:
  • 11111111.11111111.11111111.00000000 or /24 since we have 24 1.
  • Now the available hosts are just 2^8 = 256 - 2 = 254