WLAN AP ROUTER 802.11N208scope of this discussion.) These classes have different usesand characteristics.Class A networks are the Internet's largest networks, each withroom for over 16 million hosts. Up to 126 of these hugenetworks can exist, for a total of over 2 billion hosts. Because oftheir huge size, these networks are used for WANs and byorganizations at the infrastructure level of the Internet, such asyour ISP.Class B networks are smaller but still quite large, each able tohold over 65,000 hosts. There can be up to 16,384 class Bnetworks in existence. A class B network might be appropriatefor a large organization such as a business or governmentagency.Class C networks are the smallest, only able to hold 254 hostsat most, but the total possible number of class C networksexceeds 2 million (2,097,152 to be exact). LANs connected tothe Internet are usually class C networks.Some important notes regarding IP addresses:• The class can be determined easily from field1:field1 = 1-126: Class Afield1 = 128-191: Class Bfield1 = 192-223: Class C(field1 values not shown are reserved for special uses)• A host ID can have any value except all fields set to 0 or allfields set to 255, as those values are reserved for specialuses.Subnet masksDefinitionmaskA mask looks like a regular IP address, but contains a pattern ofbits that tells what parts of an IP address are the network ID andwhat parts are the host ID: bits set to 1 mean "this bit is part of thenetwork ID" and bits set to 0 mean "this bit is part of the host ID."Subnet masks are used to define subnets (what you get afterdividing a network into smaller pieces). A subnet's network ID iscreated by "borrowing" one or more bits from the host ID portionof the address. The subnet mask identifies these host ID bits.For example, consider a class C network 192.168.1. To split thisinto two subnets, you would use the subnet mask:255.255.255.128It's easier to see what's happening if we write this in binary:11111111. 11111111. 11111111.10000000As with any class C address, all of the bits in field1 throughfield3 are part of the network ID, but note how the maskspecifies that the first bit in field4 is also included. Since thisextra bit has only two values (0 and 1), this means there are twosubnets. Each subnet uses the remaining 7 bits in field4 for itshost IDs, which range from 1 to 126 hosts (instead of the usual0 to 255 for a class C address).Similarly, to split a class C network into four subnets, the maskis:
