Next, let's review some background information, including what network administrators need to know about IP addressing and subnetting. By applying the mask to a packet's destination address, routers can determine which specific network segment contains the destination host and properly deliver the packet.
![class b subnet mask table class b subnet mask table](http://4.bp.blogspot.com/-BgEaNUrLbKQ/T-i2u2BoqyI/AAAAAAAAAf0/3OaT8o6ye6I/s1600/SubNet.png)
But, as packets get closer to the destination network, routers will need more local routing information, such as the local subnet mask. Routers far away from a destination don't need much addressing detail, so routes can be summarized to a large degree. Subnetting and route summarization work together to make routers more efficient by reducing the size of routing tables. For example, a point-to-point WAN link between two routers only needs two addresses, while a LAN segment may need to support many hosts, such as servers, workstations, laptops and Wi-Fi-connected mobile devices. Subnetting enables assigned network addresses to be broken into smaller, efficient allocations that are more suitable for each network within the organization. Each subnetwork is known as an IP subnet.
![class b subnet mask table class b subnet mask table](https://www.softwaretestinghelp.com/wp-content/qa/uploads/2020/02/IPV4-subnet-list.jpg)
The result of subnetting is the number of subnetworks increases, while the number of usable host IP addresses decreases. The organization then subdivides the allocated address space into smaller allocations for each subnetwork within the organization, using a process called subnetting. Today, the allocations follow the Classless Inter-Domain Routing ( CIDR) assignment method. ISPs allocate IP address ranges to organizations based on the potential number of networks and hosts, or endpoints, that organizations require.