Which one of the following is the subnet mask equivalent of

Which one of the following is the subnet mask equivalent of /27?

A. 255.255.255.192

B. 255.255.255.224

C. 255.255.255.240

D. 255.255.255.248

Solution

OPTION B

255.255.255.224

shorthand:/25. It is 5 bit

number of addresses =2^32 WHERE hosts are 30,one bcast and 1 netbase

SOME THEORY

An IP number has four 8-bit octets. Since each binary bit has two possible values, either on or off (0 or 1), each octet can represent 2⁸ = 256 decimal numbers (0..255). If we count up all 32 bits (4x8=32), we have an Internet of 256x256x256x256 = 2³² = 4,294,967,296 possible addresses. That\'s too many for any one network; this number is segmented into more manageable chunks, or subnets, via routing. The network base address and subnet mask determines what portion of the 32-bit Internet belongs to a given subnet.The netmask shorthand notation (the /##\'s) just specifies how many 1\'s to _keep_ to determine the _network_ address of an interface. Each octet has eight 1\'s. With no masking, that\'s \"11111111.11111111.11111111.11111111\".