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Guide to TCP/IP
Fourth Edition
Chapter 10:
Transitioning from IPv4 to IPv6:
Interoperation
Objectives
• Describe the various methods that allow IPv4 and
IPv6 networks to interact, including dual stack and
tunneling through the IPv4 cloud
• Explain hybrid IPv4/IPv6 network and node types,
such as basic hybrid, nested hybrid, and true
hybrid
• Explain how an IPv6 transition address works
• Describe the various IPv4/IPv6 transition
mechanisms, such as dual stacks and IPv6-overIPv4 tunneling
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Objectives (cont'd.)
• Describe the different tunneling configuration types
and their device interactions
• Explain the ISATAP tunneling mechanism,
including its components, addressing, and routing
and router configuration
• Explain the 6to4 tunneling mechanism, including its
components, addressing and routing, and
communication procedures
• Explain the Teredo tunneling system, including its
components, addressing and routing, and
processes
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How Can IPv4 and IPv6 Interact?
• IPv6 and IPv4 will probably exist side by side for
many years
• Designers of IPv6 anticipated a slow cutover
– Created a set of techniques to allow IPv6 to function
adequately in a world dominated by IPv4
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Dual-Stack Approach
• Dual-stack
– Implementations for individuals or small offices may
work as experiments
• However, they are limited by the availability of dual
stack routers at ISPs at the edge of the Internet
• Most important dual stack machines
– Will be the routers themselves
• Dual-stack router
– Can provide a connection between the IPv4 Internet
and an office that already made the switch to IPv6
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Tunneling through the IPv4 Cloud
• Internet
– Will probably move to IPv6 “from the edges in”
• IPv6 will be adopted
– First by smaller organizations with greater flexibility
and higher tolerance for difficulties of pioneering
• IPv6 packet is formed normally
– Sent to a router capable of encapsulating it in an
IPv4 packet
• 6to4 tunneling method
– Alternate scheme specified in RFC 3056
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IPv6 Rate of Adoption
• Biggest push for the adoption of IPv6
– Coming from those who were not a part of the initial
Internet “land rush” of the 1990s
• Makers of technologies (cellular phones and
smartphones) have two reasons to embrace IPv6
– They want the address space
– Communications technologies need the improved
functionality of the IPv6 protocol suite
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Transitioning to IPv6: The Reality
• Reaction of industry participants to potential of IPv6
– Initially, service provider segment of the market
pushed for the protocol
– Router and switch vendors saw the protocol as a
marketing opportunity
– Engineers in the service provider space saw IPv6 as
a solution to solve a specific problem
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Interoperability
• One technology can work together with another
technology
• Network address translation (NAT)
– Used to provide translation between private IP
addresses and public IP addresses
• Transitioning to IPv6
– The movement of deploying IPv6 throughout a
production environment
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Network Elements
• Network elements and software tools
–
–
–
–
–
–
–
–
Clients
Servers
Routers
Gateways
VoIP networks
Network management nodes
Transition nodes
Firewalls
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Software
• Tools and utilities designed to monitor, report on,
and manage network infrastructure elements
–
–
–
–
–
–
Network management utilities
Network Internet infrastructure applications
Network systems applications
Network end-user applications
Network high-availability software
Network security software
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Transitioning to IPv6 from the
Windows Perspective
• Microsoft provides support for IPv6
implementations for:
– Windows Server 2008
– Windows Vista
– Windows 7
• Microsoft
– Supports the Intra-Site Automatic Tunnel Addressing
Protocol (ISATAP)
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Availability
• Most of the IPv6 deployments are:
– In Asia and Europe
– In areas that were behind the deployment of IPv4
infrastructures
• These environments are ahead of the curve for two
reasons
– Market is forcing IPv6 onto the consumers, which
creates demand for provider support
– A lot of the solutions are deployed initially with IPv6
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The IPv6 Address Space
• IPv6 solves address shortage problem by:
– Creating address space that is more than 20 orders
of magnitude larger than IPv4’s address space
• IPv6 address space
– Provides hierarchy in a flexible and well-articulated
fashion with room for future growth
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What’s Next?
• Major obstacle
– Convincing executive managers to deploy an IPv6
solution
• Major event that may accelerate the deployment of
IPv6
– Announcement that the Department of Defense
(DoD) will be IPv6 ready by 2012
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Hybrid IPv4/IPv6 Networks and Node
Types
• As software and hardware components are
upgraded
– IPv6 devices will need to be able to talk to each
other over an IPv4 infrastructure
• “Mixed” environments are called hybrid networks
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Basic Hybrid Network Model
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Nested Hybrid Network Model
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True Hybrid Network Model
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IPv6 Transition Addresses
• IP address parser
– Attempts to translate an IPv4 address into its IPv6
equivalent
• Transition address methods
– Using literal IPv6 addresses in URLs
– Stateless IP/ICMP translation algorithm (SIIT)
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Transition Mechanisms
• Methods and address types that provide for
communication between network nodes
– That use only IPv4 or only IPv6 to interact with each
other or with network resources
• Transition from IPv4 to IPv6 requires multiple
stages
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Dual Protocol Stacks for IPv4 and IPv6
• Implemented at the level of the device’s operating
system
• Dual-stack implementations use special addressing
• Most modern operating systems have IPv6 enabled
by default
• Dual stack and dual layer
– Different types of architecture
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Dual-IP-Layer Architecture
• Has both IPv4 and IPv6 protocols operating in a
single Transport layer implementation
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Dual-IP-Layer Architecture (cont’d.)
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Dual-Stack Architecture
• Maintains separate stacks at both the Network and
Transport layers
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Dual-Stack Architecture (cont’d.)
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Dual Architecture and Tunneling
• Dual-architecture nodes
– Can produce either IPv4 or IPv6 packets and
forward them to a gateway router
– Need two network interfaces, one for IPv4 and the
other for IPv6
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IPv6-over-IPv4 Tunneling
• Used to allow IPv6 network nodes to send packets
over an IPv4 network infrastructure
• Presents a challenge for IPv6 header construction
• Source node determines which packets must be
encapsulated
– Based on the routing information the node maintains
in its own routing table
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IPv6-over-IPv4 Tunneling (cont’d.)
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DNS Infrastructure
• DNS records and DNS name resolution
management
– Handled differently for IPv4 and IPv6
• DNS servers must be configured for dual stack
– Supporting both A and AAAA records
• In mixed IPv4/IPv6 environments
– DNS resolver libraries on network nodes must have
the ability to manage both A and AAAA records
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Tunneling Configurations for Mingling
IPv4 and IPv6
• Tunneling mechanism configurations
– Defined by RFC 4213
• Encapsulator
– Node at the sending end of the tunnel
• Decapsulator
– Receiving node at the other end of the tunnel
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Router-to-Router
• Requires specifically configured end points to the
tunnel
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Host-to-Router and Router-to-Host
• Represents the first and last legs of a packet’s trip
from source to destination
Figure 10-10 Host-to-router and router-to-host tunnels
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Host-to-Host
• Two IPv6 nodes are linked directly using a tunnel
over an IPv4 network infrastructure
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Types of Tunnels
• RFC 2893 originally specified two different
tunneling types
– Configured and automatic
• RFC 4213, which made RFC 2893 obsolete
– Removed references to automatic tunneling
• Configured tunnels
– Require that end point addresses be determined in
the encapsulator device
• From configuration data stored for each tunnel
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ISATAP
• Intra-Site Automatic Tunnel Addressing Protocol
(ISATAP)
– Used to connect dual-stack IPv4/IPv6 devices
across IPv4 network infrastructures
• Routing and Addressing in Networks with Global
Enterprise Recursion (RANGER)
– Builds on ISATAP to include IPv6 autoconfiguration
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Overview
• Implements router-to-host, host-to-router, and hostto-host address assignments
• Supported on Windows Vista, Windows 7,
Windows Server 2003, and Windows Server 2008
• ISATAP IPv6 automatic tunneling
– Can be used in domains that adhere to security
specifications found in RFC 5214
• ISATAP nodes
– Must observe functionality requirements for IPv6
computers found in RFC 4294
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ISATAP Components
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Router Discovery for ISATAP Nodes
• ISATAP interfaces
– Use neighbor discovery mechanisms described in
RFC 4861
• Because of the lack of multicast support
– Automatic router discovery cannot be used
• ISATAP hosts use PRLs to maintain current
information about ISATAP routers
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ISATAP Addressing and Routing
• ISATAP addresses use the locally administered
interface identifier
• Windows 7 or Windows Server 2008 computers
– Are automatically assigned ISATAP addresses
• Each device involved in communicating on or off an
ISATAP network
– Uses different routes to direct traffic from source to
destination nodes
• Devices and routers from other subnets need
routes to send traffic to the ISATAP logical subnet
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ISATAP Addressing and Routing
(cont’d.)
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ISATAP Communications
• ISATAP node uses host-to-host tunneling
• ISATAP host communicating with an IPv6 node on
an IPv6-capable subnet involves two different
connections
– Host-to-router tunnel
– Connection between ISATAP router and IPv6capable subnet
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Configuring an ISATAP Router
• Windows Vista/7/Server 2008 computers
– Can be configured as ISATAP routers
• ISATAP configuration is performed at the
command prompt
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Configuring an ISATAP Router
(cont’d.)
• Insert Figure 10-15 here (image quality is really
poor)
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6to4
• IPv4-to-IPv6 transition technology
– Allows IPv6 packets to be sent across IPv4 network
infrastructures, including the IPv4 Internet
– RFC 3056, current documentation
• Assigns an interim and unique IPv6 address prefix
to any site that already possesses IPv4 addresses
• Specifies encapsulation method for sending IPv6
packets over IPv4 using the unique prefix address
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Overview
• Avoids the need to configure the distinct tunnels
required by ISATAP
• Applied to a network node or to a local network
• 6to4 addressing on an IPv6 network employs
autoconfiguration
– Uses the last 64 bits as the host address and the
first 64 bits as the IPv6 prefix
• 6to4 issues
– Large numbers of misconfigured nodes
– Poor network performance
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6to4 Components
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6to4 Addressing and Routing
• Any 6to4 site must possess at least one valid
globally unique 32-bit IPv4 address
• 6to4 gateway router directly attached to the
Internet
– Receives an IPv4 address assignment from a
service provider
– Address represents the site address
• 6to4 network devices use on-link and default routes
• 6to4 relay uses on-link route on its tunneling
interface to perform router-to-router communication
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6to4 Communication
• Communication models in a 6to4 infrastructure
– Node-to-node/router
– Node-to-node
• Communication between 6to4 node and IPv6 host
must go
– From sending node to router
– From router to relay
– From relay to receiving node
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Using ISATAP and 6to4 Together
• Normally, an ISATAP host could not receive
advertisements from a 6to4 router
– 6to4 router could also be manually configured as an
ISATAP router
• ISATAP node then configures a default route to the
6to4 router in order to send traffic
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Teredo
• IPv4-to-IPv6 transition technology
– Allows IPv6 connections between two IPv6 network
nodes across an IPv4 network infrastructure
• Can operate from behind home routers and
broadband devices
– Using network address translation (NAT)
• Developed by Microsoft
– Formally standardized by RFC 4380
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Overview
• Teredo service tunnels IPv6 packets over IPv4
UDP
– Using Teredo servers and Teredo relays
• Teredo servers are stateless
– Responsible for managing only small amounts of
traffic between Teredo client computers
• Teredo relays
– Perform IPv6 routing between the Teredo service
and IPv6-capable networks
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Teredo Components
• Essential components of a Teredo system
–
–
–
–
Teredo client
Teredo server
Teredo relay,
Teredo host-specific relay
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Teredo Addressing and Routing
• Teredo addresses are made up of five
components:
–
–
–
–
–
Prefix
Server IPv4
Flags
Port
Client IPv4
• Like other IPv4/IPv6 transition mechanisms
– Teredo uses online and default routes
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Teredo Processes
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Summary
• During the transition from IPv4 to IPv6, there will be
a lengthy period of time when both protocols exist
side by side
• Several different IPv4/IPv6 hybrid networks and
nodes can be used to facilitate the transition
• Transition mechanisms can use a dual-IP-layer
architecture or a dual-stack architecture
• IPv6-over-IPv4 tunneling involves different device
configurations
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Summary (cont'd.)
• ISATAP is an automatic tunneling mechanism that
allows IPv6 ISATAP network nodes to
communicate across an IPv4 network
• 6to4 is an IPv4-to-IPv6 transition technology
characterized by its ability to allow IPv6 packets to
be sent across IPv4 networks and the use of relay
servers
• Teredo is another IPv4-to-IPv6 transition
technology characterized by its unique ability to
operate behind routers and broadband devices with
NAT enabled
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