If you are borrowing 2 bits, then the subnet masks will look like:
255.192.0.0 Class A
255.255.192.0 Class B
255.255.255.192 Class C
Same as subnetting any other class, or a classless network. From the bits originally reserved for the host (16 bits, in the case of a class B address), you "borrow" some bits, that is, you use them to specify the subnet. The remaining bits specify an individual host within a subnet.
255.0.0.0
Since a subnet mask is used to separate the network id from the host id, any 1 bits indicate the network portion and the 0 bits indicate host portion. As an example, in the subnet mask: 255.255.0.0 This indicates the first two octets are used for the network, and the last two octets (ipV4) are used for host portion of an address.
You must extract the first 8 bits of the host address (since the subnet mask has the first 8 bits equal to 1), and set all others to zero. The answer in this case is 86.0.0.0.You must extract the first 8 bits of the host address (since the subnet mask has the first 8 bits equal to 1), and set all others to zero. The answer in this case is 86.0.0.0.You must extract the first 8 bits of the host address (since the subnet mask has the first 8 bits equal to 1), and set all others to zero. The answer in this case is 86.0.0.0.You must extract the first 8 bits of the host address (since the subnet mask has the first 8 bits equal to 1), and set all others to zero. The answer in this case is 86.0.0.0.
There are 16 bits available; it is up to you how many of those bits you reserve for the subnet, and how many for the individual hosts within each subnet.
Subnet Mask
This assumes you know how to subnet. On a network with 190.254.0.0 as a host address and using 11 bits for the subnet mask. The network address is 190.224.0.0 and the end of the range is 190.255.255.224. The address you show is within this range so cannot be the network address. If you don't know how to work this out manually use a subnet calculator such as the one on this URL: http://www.boson.com/FreeUtilities.html
If you mean the range of IP addresses in the subnet, additional information is required. Specifically, the subnet mask.
151.242.16.49 would be class B in a classful environment with a network mask of 16 bits. An additional 7 bit subnet mask puts the total mask at 23 (i.e.: 255.255.254). Subnet ID would be: 151.242.16.0 Host address range: 151.242.16.1 through 151.242.17.254 Subnet Broadcast address would be: 151.242.17.255
From the 16 bits reserved for the host, you "lend" 3 bits for the subnet. That gives you the possibility of dividing into eight subnets. The remaining 13 bits indicate the host in each subnet. - To see the complete steps in more detail, do some Internet searching on subnetting.
Subnet mask.
By default Class C subnet mask is 255.255.255.0 = 24 bits for network id and 8 bits for host id. in Binary 1111 1111. 1111 1111. 1111 1111. 0000 0000 Here all 1s are Network bits and all 0s are host bits. For this subnet mask you can have 256 hosts. And you can use 254 host and asign IP address to them. By Saurabh