Chapter 6

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.0
Using IP Addressing in
the Network Design
Designing and Supporting Computer Networks – Chapter 6

© 2006 Cisco Systems, Inc. All rights reserved. Cisco Public 2
Objectives
 Describe the use of a hierarchical routing and
addressing scheme
 Create the IP address and naming scheme to support
growth and efficient routing protocol operation
 Describe IPv6 implementations and IPv6 to IPv4
interactions
 Implement IPv6 on a Cisco device

Describe the Use of a Hierarchical
Routing and Addressing Scheme
Functions of a hierarchical addressing scheme:
 Prevent duplication of addresses
 Control access, monitor security and performance
 Support modular design and scalability

 Poorly-planned IP addressing can result in
discontiguous subnets
 Routing protocols may display more than one summary
route to discontiguous subnets
 Manual configuration of routing protocols may be
required

 VLSM provides more efficient use of IP address space
 VLSM enables routers to summarize routes on
classless boundaries

 CIDR ignores classful boundaries
 CIDR enables supernets: VLSMs with shorter prefix
lengths than the defaults
• Summarization produces leaner routing tables

Create the IP Address and Naming
Scheme
 Plan the entire
addressing scheme in
advance
 Allow for significant
growth
 Support the physical
layout, routing, and
security

Scheme
 Define the addressing blocks scheme to support
summarization
 Document locations, VLAN or network type, and
number of hosts and networks

Scheme
 Select the
appropriate routing
protocol to use in the
network
 Support classless
routing and VLSM
 Small and infrequent
updates to reduce
traffic
 Fast convergence

Factors in designing the routing strategy:
 Load balancing
 Authentication
Scheme

Scheme
 Determine when and how to summarize address space
for efficient routing

Scheme
 Design an address scheme for an internetwork and
assign ranges for hosts, network devices, and the
router interface

Scheme
 Determine an appropriate naming scheme
 Use codes and avoid names that easily identify
protected resources
 Maintain consistency
 Document the names

Describe IPv6 Implementations and IPv6
to IPv4 Interactions
Enhancements available with IPv6:
 Mobility and security
 Simpler header
 Address formatting

Common transition
methods from IPv4 to
IPv6:
 Dual stack
 Tunneling
 Proxying and
translation

How to configure IPv6 on a Cisco device:
 Activate IPv6 forwarding
 Configure interfaces
 Configure name resolution

RIPng for IPv6:
 The tag parameter in
interface configuration
mode
 The ipv6 rip name enable
command on directly-
connected routers

Summary
 Allocation of IP addresses must be planned and
documented.
 A properly-designed hierarchical IP addressing scheme
makes it easier to perform route summarization.
 A complex hierarchy of variable-sized networks can be
summarized at various points using a prefix address.
 The choice of routing protocol must support the VLSM
and summarization strategy.
 A good network naming scheme makes the network
easier to manage and easier to navigate.
 IPv6 addresses are written as a series of eight 16-bit
hexadecimal digits separated by colons.

Chapter 6

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