WHAT IS THE SUBNET MASK..

Question

An organization having class A network wants a subnet for 510 departments.The subnet mask should be?

Answer 1

since it is a class A network so , first byte will be used for network id and the rest 3 byte will be used for subnet and host id.

Since , there should be 510 departments and hence the address space of the network should be divided into 510 parts.

so,the lefstmost 9 bit  of the 3 byte will be 1 as it will be fixed to divide the add space in 512 parts.

Note - each 1 in the binary no divide it in 2 regions.

so,required subnet mask = 11111111   11111111  10000000  00000000

subnet mask is 255.255.128.0

Comments

but I deciphered that each subnet should contain 510 hosts....so if this is the case then 9 bits from LSB should be zero as we want 2^9-2=510 hosts ..therefore the SM should be 11111111 . 11111111 . 11111110 . 00000000

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i think the n/w is divided into 510 subnet .

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subnet mask is 255.255.128.0