Which of the following is NOT a valid subnet mask?

Which of the following is NOT a valid subnet mask?

Step 1: Understand what a subnet mask is. A subnet mask is used in networking to divide an IP address into a network and host part.
Step 2: Know that a subnet mask is made up of four numbers (octets), each ranging from 0 to 255.
Step 3: Check the values in the subnet mask. Each octet must be between 0 and 255.
Step 4: Identify the subnet mask in question, which is 255.255.255.256.
Step 5: Look at the last octet (256) and see if it is within the valid range (0-255).
Step 6: Since 256 is greater than 255, it is not a valid value for a subnet mask.
Step 7: Conclude that 255.255.255.256 is NOT a valid subnet mask.

No concepts available.