217

Figure 6-21  Example Network to Subnet

Corporate HQ = 500	Legal Office = 20
172.16.0.0/23	172.16.3.64/27
	WAN3 = 2
WAN1 = 2	WAN2 = 2
HR Office = 50	Sales Office = 200
172.16.3.0/26	172.16.2.0/24

Determine the Number and Size of the Networks

For this internetwork, consider the number of networks and the number of hosts in each network. The network is subnetted to overcome issues with location, size, and control. In designing the addressing, consider the factors for grouping the hosts that we discussed previously:

■   Grouping based on common geographic location

■   Grouping based on hosts used for specific purposes

■   Grouping based on ownership

Each WAN link is a network. You create subnets for the WAN that interconnect different geographic locations. When connecting the different locations, you use a router to account for the hardware differences between the LANs and the WAN.

Although hosts in a common geographic location typically comprise a single block of addresses, you might need to subnet this block to form additional networks at each location. You need to create subnetworks at the different locations that have hosts for common user needs. You might also have other groups of users that require many network resources, or