A network administrator is adding a new LAN to a branch office. The new LAN must support 61 connected devices. What is the smallest network mask that the network administrator can use for the new network?

To support 61 connected devices, you need a subnet that can provide at least 61 usable IP addresses (remembering that in any given subnet, two IP addresses are always used up – one for the network address and one for the broadcast address).

Here’s how the subnet masks break down in terms of number of available hosts:

• 255.255.255.224 – This is a /27 subnet mask, which allows for 32 addresses in total, but with 2 addresses used for network and broadcast, you get 30 usable addresses.
• 255.255.255.240 – This is a /28 subnet mask, which allows for 16 addresses in total, with 14 usable addresses.
• 255.255.255.192 – This is a /26 subnet mask, which allows for 64 addresses in total, but with 2 addresses used for network and broadcast, you get 62 usable addresses.
• 255.255.255.128 – This is a /25 subnet mask, which allows for 128 addresses in total, with 126 usable addresses.

The smallest subnet mask that will support 61 connected devices, allowing for the network and broadcast addresses, is 255.255.255.192 or a /26 subnet mask. This will allow for 62 usable IP addresses, just enough for the 61 devices needed.