YES!
netmask is just another way to say subnet mask. crazy but confusing.
Subnet Mask provides Network & Class Identificationfor an IP Address.
Smaller than 65.56.0.0/14. With just the IP, there is no way to know the netmask. We can see that Level 3 owns that address and their block is a /14. It could be a /30 with a gateway of 65.56.25.18. it could be a /29 with a gateway of 65.56.25.18-22. In short, there is no way to definitively know the netmask from the IP only.
Subnet mask defines our network bit . If we are using a single network then all computers should have same subnet mask as well as the ip address, that belongs to the same network id.
No. 192.168.12.1 - 192.168.12.254 is one subnet (assuming 255.255.255.0 subnet mask)
To determine if Computer 1 and Computer 2 belong to the same subnet, you need to compare their IP addresses and subnet masks. If the network portion of their IP addresses, as defined by the subnet mask, matches, then they are in the same subnet. For instance, if Computer 1 has an IP address of 192.168.1.10 with a subnet mask of 255.255.255.0, and Computer 2 has an IP address of 192.168.1.20 with the same subnet mask, they are in the same subnet. If the network portions differ, they belong to different subnets.
/24 in CIDR 255.255.255.0 in netmask.
If the other PC is on the same LAN segment then it will have the same subnet mask as yours. A subnet mask is the same for all subnets within a network so that will be the same as well. For other networks it isn't important to know what their subnet is. You could always ask the other user to find out that information if you needed to know.
No, all subnets must use the same subnet mask
The default subnet mask for this address - a class A address - is 255.0.0.0 (same as /8).
It does not require a subnet mask.
To accommodate 310 hosts in a subnet, you would need a netmask that provides at least 512 IP addresses, as the number of usable host addresses is calculated as (2^{(32 - n)} - 2), where (n) is the number of bits used for the network portion. A /23 netmask (255.255.254.0) allows for 512 total IP addresses, resulting in 510 usable addresses after subtracting the network and broadcast addresses. Thus, a /23 netmask is suitable for a subnet requiring 310 hosts.
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.