IP addresses are structured as four groups of 3 decimal numbers i.e. 111.222.333.444.Each three decimal group of numbers is called an octet because converting the decimal form to binary results in an 8-bit number.

Note:

1. aaa bbb ccc ddd are any numbers between 0 and 255
2. 127 in the 1st octet of Network ids reserved for diagnostics.
3. 255 and 0 in 4th octet of Host ids reserved for Broadcast and Network addresses.

Private IP addresses

Class	Network ID's
A B C	10.0.0.0 --> 10.255.255.255 172.16.0.0 --> 172.31.0.0 192.168.0.0 --> 192.168.255.255

 
These addresses should only be used on private networks not connected to the Internet
 

Used to separate the network ID from the host ID for routing purposes. Once the network and host IDs are derived from the TCP/IP address, it is a simple matter to determine if the address is local or remote.

Two Hosts, same subnet?

With default subnet masks, it's a simple mater of looking at the TCP/IP address to determine if two hosts are on the same network. If the network has been divided into subnets the conclusion is not so evident.
 
Before we begin we should define a bitwise AND operation and a method for converting binary to decimal.
 
Truth Table - Bitwise AND

Bit 1	Bit 2	Bit 1 AND Bit2
0 0 1 1	0 1 0 1	0 0 0 1

Converting binary to decimal

This table represents an 8-bit octet with the place value for each bit

8	7	6	5	4	3	2	1	Low order bit
128	64	32	16	8	4	2	1	Place value

 
So, to find the decimal value of the binary number 11000010, we multiply each bit by its place value.
 

1	1	0	0	0	0	1	0	Binary Number
1x128	1x64	0x32	0x16	0x8	0x4	1x2	0x1	Binary No. X Place value
128	64	0	0	0	0	2	0	Sum

 
The decimal number is derived by adding the sums:
128 + 64 + 0 + 0 + 0 + 0 + 2 + 0 = 194
 
So we see that the decimal value 194 is equal to the binary number 11000010
 

Determining the subnet

Step 1. Convert the decimal numbers of the first address to binary:

We conclude that the first host 192.168.110.19 resides on subnet 194.168.110.2
 
 
Step 2. Converting the second host's address:

We conclude that the second host 192.110.110.56 resides on subnet 194.168.110.32
 
The two hosts clearly do not reside on the same subnet.