A submask is designed to separate the network id portion of an IP address from the host or client portion. This helps a router determine whether the packet needs to be forwarded to another network.
The subnet mask separates the network id from the client id in the IP address for a sender or receiver.
There is no technical term called "subnet mass number." It might be a misconstrued term. Subnetting is dividing a network into smaller subnetworks for better organization and security. Mass number is used in chemistry to denote the total number of protons and neutrons in an atom's nucleus.
It does not require a subnet mask.
If this is a default subnet mask, then it would be a class C subnet mask. If you are subnetting a network and this is not the default subnet mask, then it could be either a class A or class B.
The default subnet mask has a standard size. The custom subnet mask allows you to make subnets that are smaller or larger than the default.
2 given subnets
255.255.255.0
255.255.255.0
The default subnet mask would be 255.255.0.0 for a class B address.
if the ip address is 192.168.2.1 then the subnet mask should be 255.255.255.0
Subnet mask for the above is 255.0.0.0
To create a subnet ID, you start with the network's base IP address and subnet mask. The subnet mask determines how many bits are allocated for the network and how many for the hosts. By applying the subnet mask to the base IP address, you can identify the subnet ID, which represents the network portion of the address. For example, if your base IP is 192.168.1.0 with a subnet mask of 255.255.255.0, the subnet ID is 192.168.1.0.