CHAPTER - 5

SUBNET MASK

255.255.255.255   =  32 Bit

This form derived from 

128+64+32+16+8+4+2+1 = 255

The above is considered as 8 bit.

Four 8 Bits are combines to 32 bit.

Class A - Address  

8 Bit  Network Address by default.  

255.0.0.0 Subnet mask by default.

Class B - Address

16 Bit Network Address by default

255.255.0.0

Class C - Address

24 Bit Network Address By default

255.255.255.0

TO Start From Previous Chapter

http://uniqskills.blogspot.in/2016/08/CCNA-INDEX.html

https://uniqskills.blogspot.in/2016/08/ccna-details.html

https://uniqskills.blogspot.in/2016/08/chapter-3ipaddressing.html

https://uniqskills.blogspot.in/2016/08/chapter-4.html

http://uniqskills.blogspot.in/2016/08/ccna-questions-1.html