It also provides the ideal structure for overlaying a hierarchical IP
addressing scheme. Following are some guidelines:
?– Design the IP addressing scheme so that blocks of 2n contiguous network numbers
(such as 4, 8, 16, 32, 64, and so on) can be assigned to the subnets in a given building
distribution and access switch block. This approach lets you summarize each switch
block into one large address block.
?– At the building distribution layer, continue to assign network numbers contiguously to
the access layer devices.
?– Have a single IP subnet correspond to a single VLAN. Each VLAN is a separate
broadcast domain.
?– When possible, subnet at the same binary value on all network numbers to avoid
variable-length subnet masks. This approach helps minimize errors and confusion
when troubleshooting or con?¬?guring new devices and segments.
Figure 2-3 shows how this architectural model is deployed and illustrates IP address
allocation between various groups in the enterprise. You will notice that each building has
unique subnets. Each of these subnets would be assigned to a single VLAN. Each building
has been assigned a range with four IP subnets even though only two departments are
shown.
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