What determines the size of a group of servers in the same subnet?

The size of a group of servers in the same subnet is determined by the Classless Inter-Domain Routing (CIDR) block. CIDR allows for more efficient allocation of IP addresses by permitting variable-length subnet masking. When a CIDR block is defined, it specifies the range of IP addresses that can be assigned within that subnet, thereby determining how many devices (or servers) can effectively reside in that specific subnet.

For example, if a subnet is defined with a CIDR notation of /24, this indicates that there are 256 possible addresses available (from 0 to 255), although some are reserved for network and broadcast addresses, so the total usable addresses would be 254. The CIDR block thus directly influences the number of servers that can be managed within that subnet by dictating how many unique IP addresses are available.

The other options, while related to networking, do not determine the size of a subnet. The default gateway is a device that routes traffic from the subnet to other networks but does not influence how many devices can reside within the subnet itself. DNS (Domain Name System) translates domain names to IP addresses but does not affect the subnet's size. Similarly, NTP (Network Time Protocol) synchronizes clocks on devices