What is the subnet address when ip address is 142.80.119.128?

Answer 1

The subnet Mask I presume you mean.

There is no single SET subnet mask for any IP

The subnet mask for most general home networks is 255.255.255.0

The subnet mask is identified by the third set of numbers in the IP address when converted to binary.

Answer 2

There is no one subnet mask that can be set for this IP address today. However, if we assume for a moment that the question is in regard to the old style of classed IP address assignment (which was discontinued in 1993 in favor of Classless Inter-Domain Routing (CIDR)), then this address would be a Class B address. This means that only the first two octets are assigned. So, based on this, the available addresses in this range would be between 142.80.0.0 and 142.80.255.255. As such, the subnet mask for this (and any other Class B assignment) would be 255.255.0.0.

The old idea of classed IP address allocation set up certain address ranges as Class A, B, or C with D being defined but unused and E being undefined and reserved for future use. The idea was that the largest organizations would be granted Class A addresses assignments which would allow them to use up to 16,777,216 addresses for their network, which would be more than enough for any organization to be able to get all of its devices visible and accessible through the internet. Class B was destined for assignment to smaller organizations that needed only 65,536 addresses. Class C was typically assigned to yet smaller organizations such as schools and companies that needed only 256 available addresses. However, as one can probably readily see, there were and still are very few companies in the world that would use all of a Class A or B IP address range, so many of the addresses were wasted and that directly contributed to the very quick depleting of available addresses for others to use. As such, CIDR was implemented and IP addresses are now assigned as needed rather than as big blocks.

With the forthcoming IP version 6 addressing scheme (which has a total of six numbers in an address rather than just four), available address concerns will not be a major issue since that would allow a total of over 281 billion addresses to be available, thus giving every person on the planet 40,000 publically available IP addresses on average. No private person will need that many for any reason, so this will solve our problem for quite awhile.