* A network address is an identifier that specifies a group of devices that share a common network prefix.
A network address is usually written in dotted decimal notation, such as 80.87.78.0, and is followed by a slash and a number that indicates the length of the network prefix in bits, such as /26. This notation is called CIDR (Classless Inter-Domain Routing) and allows for flexible subnetting of IP networks.
* A host address is an identifier that specifies a single device within a network. A host address is derived from the network address by filling the remaining bits after the network prefix with either zeros or ones.
A host address is also written in dotted decimal notation, such as 80.87.78.1, and is usually the lowest or the highest possible value within the network range.
* To describe a network, we need to know the range of valid host addresses that belong to that network.
To find the range, we need to perform the following steps:
* Convert the network address and the subnet mask to binary form. The subnet mask is a 32-bit value that has the same number of ones as the network prefix length, followed by zeros. For example, /26 corresponds to 11111111.11111111.11111111.11000000 in binary.
* Perform a bitwise AND operation between the network address and the subnet mask to get the network prefix in binary form. This is the common part of all host addresses in the network. For example, 80.87.78.0 in binary is 01010000.01010111.01001110.00000000, and the result of the AND operation is 01010000.01010111.01001110.00000000, which is the same as the network address.
* Find the lowest and the highest possible host addresses by changing the remaining bits after the network prefix to either zeros or ones, respectively. For example, the lowest host address is obtained by changing the last 6 bits to zeros, which gives
01010000.01010111.01001110.00000001, or 80.87.78.1 in decimal. The highest host address is obtained by changing the last 6 bits to ones, which gives
01010000.01010111.01001110.00111110, or 80.87.78.62 in decimal.
* The range of valid host addresses is the interval between the lowest and the highest host addresses, inclusive. For example, the range for the network 80.87.78.0/26 is 80.87.78.1 -
80.87.78.62.
* Based on the above steps, we can conclude that option C is the correct answer, as it describes the network 80.87.78.0/26 with the correct range of host addresses. The other options are incorrect because they either have the wrong network address, the wrong network prefix length, or the wrong host address range. References:
* CompTIA Network+ N10-008 Study Guide, Chapter 2: Network Devices and Technologies, Section
* 2.6: Network Addressing, Subsection: IPv4 Addressing, pp. 102-105.
* Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 2.7: Network Addressing, Subsection: Subnetting, p. 39.
* IP Subnet Calculator, Calculator.net.