Subnet Mask Explained | CompTIA Network+ N10-008

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A Subnet mask is given to each computer on the network to recognize if a packet is for the LAN or for a computer on the WAN. A subnet mask is a string of zeros and ones totaling to thirty-two bits for example: 11111111. 11111111. 11111111.00000000 in decimal is 255.255.255.0.

To get a network ID portion of an IP address, line up the IP address and its corresponding subnet mask in binary, the portion of the IP address that aligns with the ones of subnet mask is the network ID while the portion that aligns with the zeros is the host ID.

Some of the commonly used subnet masks are:
11111111111111111111111100000000 255.255.255.0
11111111111111110000000000000000 255.255.0.0
11111111000000000000000000000000 255.0.0.0

These subnet masks are known as classful subnetting. These classful subnetting is used to describe to traditional class block which are Classful A,B,C,D and E addressing

A class A network block has a network ID starting from between 1 and 126 while a class B network block has a network ID starting from between 127 and 191 while a class C network block has a network ID starting from between 192 and 223 while a class D network block is used for multicasting and class E network is used mostly for experimental purposes only like research.

#subnetmask ,#network ,#comptia

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