Why subnet mask is neceessary?

Subnetting is essentially the modification of a single IP network to create two or more logically visible sub-sections. It entails changing the subnet mask of the local network number to produce an even number of smaller network numbers, each with a corresponding range of IP addresses. Subnetting is required when one network number needs to be distributed across multiple LAN segments. This may be the case in instances when: * A company uses two or more types of LAN technology (for example, Ethernet, Token Ring) on their network.

* Two network segments are restricted by distance limitations (for example, remote offices linked via point-to-point circuit).

* Segments need to be localized for network management reasons (accounting segment, sales segment, etc.).

* Hosts which dominate most of the LAN bandwidth need to be isolated.