Information Technology Reference
In-Depth Information
VLSM Address Assignment: Example 2
Because this is an important topic, here is another example of VLSM design. Take net-
work 10.0.0.0/8, which is commonly used by companies in their internal networks because
this is private IP address space.
Global companies divide this address space into continental regions for the Americas, Eu-
rope/Middle East, Africa, and Asia/Pacific. An example is shown in Table 8-25, where the
address space has been divided into four major blocks:
10.0.0.0 to 10.63.0.0 is reserved.
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10.64.0.0 to 10.127.0.0 for the Americas.
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10.128.0.0 to 10.191.0.0 for Europe, Middle East, and Africa.
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10.192.0.0 to 10.254.0.0 for Asia Pacific.
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Ta b l e 8 - 2 5
Global IP Address Allocation
Region
Network
Reserved
10.0.0.0/10
North America
10.64.0.0/10
South America
10.96.0.0/11 *part of the above
Europe/Middle East
10.128.0.0/10
Africa
10.160.0.0/11 *part of the above
Asia Pacific
10.192.0.0/10
From each of these regions, address blocks can be allocated to company sites. Large sites
may require 4, 8, or 16 Class C equivalent (/24) subnets to assign to data, voice, wireless,
and management VLANs. Table 8-26 shows an example. The large site is allocated net-
work 10.64.16.0/20. The first four /24 subnets are assigned for data VLANs, the second
four /24 s ubnets are as s ig ned for voice VL ANs, and the third four /24 s ubnets are as s ig ned
for w irele s s L AN VL ANs. O ther s ubnets are u s ed for router and s w itch interface s, point-
to-point links, and network management devices.
Ta b l e 8 - 2 6
IP Address Allocation in a Large Site
Function
IP Subnet
Data VLAN 1
10.64.16.0/24
Data VLAN 2
10.64.17.0/24
Data VLAN 3
10.64.18.0/24
Data VLAN 4
10.64.19.0.24
Vo i c e V L A N 1
10.64.20.0/24
Vo i c e V L A N 2
10.64.21.0/24
