Calculating Usable Hosts on the .128.0/19 Network

D

The .128.0/19 network refers to a block of IP addresses with a subnet mask of 255.255.224.0.

To determine the number of usable hosts on this network, we need to first calculate the total number of IP addresses in the block using the formula:

2^(32-subnet mask) - 2

In this case, the subnet mask is 19, so we get:

2^(32-19) - 2 = 2^13 - 2 = 8190

This means that there are 8190 IP addresses in the .128.0/19 network.

Next, we need to determine the range of usable host addresses within this network. The usable host addresses are the addresses that can be assigned to devices on the network, excluding the network address (which is .128.0) and the broadcast address (which is .143.255).

To find the first usable host address, we add 1 to the network address:

.128.0 + 1 = .128.1

To find the last usable host address, we subtract 1 from the broadcast address:

.143.255 - 1 = .143.254

Therefore, the range of usable hosts on the .128.0/19 network is .128.1 through .143.254.

So the correct answer is A. .128.1 through .143.254.