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If a class $B$ network on the Internet has a subnet mask of $255.255.248.0$, what is the maximum number of hosts per subnet?

1. $1022$
2. $1023$
3. $2046$
4. $2047$

a number of zeros are to be counted for calculating the total number of possible hosts per subnet.

$255-248 = 7$ can be represented using $3\;\text{bits}$

these $3\;\text{bits} + 8\;\text{bits}$ more $= 11\;\text{bits}$

So, possible subnets $= 2^{11}$ out of these $2$ are reserved as subnet $\text{ID}$ and $\text{DBA}$

Therefore, we have maximum possible usable hosts $= 2^{11}-2 = 2046$

Correct Answer: $C$

what does 'per subnet' means then ?
per subnet means here it is class B network , so no of network bits is known so we can know no of subnet bits. In which each subnet can have many hosts . Here many subnets are possible so per subnet means in each subnet how many hosts are present
What does DBA stand for? I have seen this word on many computer networks answers on this site

When a host in a network wants to send a data packet to all other hosts in another network then the address will be = NID.255.255.255
we all know that a class b network in general has 16 bits for network ID and 16 bits for host ID but subnet mask is given as to 48 in the third octet that means all the five bits are occupied that means we will have 30 subnets possible subnetworks can be made now only 3 bits from the third of data remaining and entire 4th Octet is remaining that means we have 11 bits for host now we are asked in the question that how many hosts per subnet we can form the answer is 2 to the power 11 - 2 that is 2046 that is the answer
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