A network administrator is adding a new LAN to a branch office. What is the smallest network mask that can support 90 connected devices?

A network administrator is adding a new LAN to a branch office. What is the smallest network mask that can support 90 connected devices?

• A. 255.255.255.0
• B. 255.255.255.128
• C. 255.255.255.192
• D. 255.255.255.240

Answer: (B)

To determine the smallest network mask that can support 90 connected devices, it's important to understand how subnetting works and how to calculate the number of usable IP addresses in a given subnet. The number of usable IP addresses in a subnet can be calculated using the formula \(2^n - 2\), where \(n\) represents the number of bits available for host addresses. The subtraction of 2 accounts for the network address and the broadcast address, which cannot be assigned to hosts. First, let's see how many addresses each option provides: - A subnet mask of 255.255.255.0 (/24) provides \(2^8 - 2 = 254\) usable addresses. This can support 90 devices. - A subnet mask of 255.255.255.128 (/25) provides \(2^7 - 2 = 126\) usable addresses. This can also support 90 devices. - A subnet mask of 255.255.255.192 (/26) provides \(2^6 - 2 = 62\) usable addresses. This cannot support 90 devices, so it is too small. - A subnet mask of 255.255.255.240 (/28) provides

To determine the smallest network mask that can support 90 connected devices, it's important to understand how subnetting works and how to calculate the number of usable IP addresses in a given subnet.

The number of usable IP addresses in a subnet can be calculated using the formula (2^n - 2), where (n) represents the number of bits available for host addresses. The subtraction of 2 accounts for the network address and the broadcast address, which cannot be assigned to hosts.

First, let's see how many addresses each option provides:

• A subnet mask of 255.255.255.0 (/24) provides (2^8 - 2 = 254) usable addresses. This can support 90 devices.

• A subnet mask of 255.255.255.128 (/25) provides (2^7 - 2 = 126) usable addresses. This can also support 90 devices.

• A subnet mask of 255.255.255.192 (/26) provides (2^6 - 2 = 62) usable addresses. This cannot support 90 devices, so it is too small.

• A subnet mask of 255.255.255.240 (/28) provides