Summarization

Having assigned IP addressing based on a hierarchical design, you can now consider the full weight of the advantages. The primary advantage is the reduction in network traffic and the size of the routing table.

Summarization allows the representation of a series of networks in a single summary address.

The reasons that the Internet implemented CIDR are equally pertinent in a single organization. VLSM and CIDR use the same principles, with VLSM just being an extension of CIDR at the organizational level.

At the top of the hierarchical design, the subnets in the routing table are more generalized. The subnet masks are shorter because they have aggregated the subnets lower in the network hierarchy. These summarized networks are often referred to as supernets, particularly when seen in the Internet as an aggregation of class addresses. They are also known as aggregated routes. Figure 3-9 shows the physical network design for the case study discussed earlier. Figure 3-10 shows the allocation of addresses using VLSM to support summarization for this network design.

Figure 3-9 The Application of Summarized Routes on a Hierarchically Designed Network

Figure 3-9 The Application of Summarized Routes on a Hierarchically Designed Network

Building 2 140.100.50.0/24

Figure 3-10 The Binary Calculation of the Hierarchical Addressing for the Organization

NIC number

140.100.0.0

Region

000 140.100.0.0/19

010 140.100.84.0/19

011 140.100.96.0/19

100 140.100.126/19

101 140.100.160.0/19

110 140.100.182.0/19

111 140.100.224.0/19

Campus

001/00 01 10 11

140.100.32.0/21 140.100.40.0/21 140.100.48.0/21 140.100.66.0/21

Building

001/10/000 001 010 011 100 101 110 111

140.100.48.0/24 140.100.49.0/24 140.100.50.0/24 140.100.51.0/24 140.100.52.0/24 140.100.53.0/24 140.100.54.0/24 140.100.55.0/24

Floor

001/10/010./000 001 010 011 100 101 110

140.100.50. 140.100.50. 140.100.50. 140.100.50.1 140.100.50.1 140.100.50.1

Hosts

001/10/010/100/00000

140.100.50.128

00001

140.100.50.129

00010

140.100.50.130

00011

140.100.50.131

00100

140.100.50.132

00101

140.100.50.133

00110

140.100.50.134

00111

140.100.50.135

01000

140.100.50.136

01001

140.100.50.137

01010

140.100.50.138

01011

140.100.50.139

01100

140.100.50.140

01101

140.100.50.141

01110

140.100.50.142

01111

140.100.50.143

10000

140.100.50.144

10001

140.100.50.145

10010

140.100.50.146

10011

140.100.50.147

10100

140.100.50.148

10101

140.100.50.149

10110

140.100.50.150

10111

140.100.50.151

11000

140.100.50.152

11001

140.100.50.153

11010

140.100.50.154

11011

140.100.50.155

11100

140.100.50.156

11101

140.100.50.157

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