# All-zeros subnet and All-ones subnet

It is said that practically all-zeros and all-ones subnets are not used.

Let us consider an a network $$200.200.13.13/25$$

Here Network ID is represented by using $$25$$ bits and Host ID using $$32-25=7$$ bits.

Binary Representation : $$11001000.11001000.00001101.00000000$$

Last 7 bits which represent HID are $$0000000$$

Suppose we want to divide the network into $$4$$ subnets, so we will borrow $$2$$ bits from Host.

So the subnets will be

$$11001000.11001000.00001101.00000000$$ - $$200.200.0.0/27$$

$$11001000.11001000.00001101.01000000$$ - $$200.200.0.64/27$$

$$11001000.11001000.00001101.10000000$$ - $$200.200.0.128/27$$

$$11001000.11001000.00001101.11000000$$ - $$200.200.0.192/27$$

Now it is said that all-zeros and all-ones subnets are not used, then let us consider -

(i) the IP addresses ranging from $$200.200.0.0 - 200.200.0.63$$ which should belong to all-zeros subnet and

(ii) the IP addresses ranging from $$200.200.0.192 - 200.200.0.255$$ which should belong to all-ones subnet

Will belong to which subnet/network or will remain unallocated ?