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Bits and Decimal Values in an Octet
 

	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Binary Bits	1	1	1	1	1	1	1	1
Power of 2	2 to the 7th	2 to the 6th	2 to the 5th	2 to the 4th	2 to the 3rd	2 to the 2nd	2 to the 1st	2 to the 0
Decimal	128	64	32	16	8	4	2	1

Converting 210 Decimal to 11010010 Binary
 

	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Decimal	128	64	0	16	0	0	2	0
Binary Bits	1	1	0	1	0	0	1	0

    Converting Binary to Decimal can be accomplished by using a table as show above in reverse order.
 

Important Powers of 2  (These are the only numbers you will ever see in a subnet mask)
 

• The Decimal 128 equals 10000000 in binary.
• The Decimal 192 equals 11000000 in binary
• The Decimal 224 equals 11100000 in binary
• The Decimal 240 equals 11110000 in binary
• The Decimal 248 equals 11111000 in binary
• The Decimal 252 equals 11111100 in binary
• The Decimal 254 equals 11111110 in binary
• The Decimal 255 equals 11111111 in binary