Windows® 7 Resource Kit Mitch Tulloch, Tony Northrup,

Windows® 7 Resource Kit Mitch Tulloch, Tony Northrup,
Windows® 7 Resource
Kit
Mitch Tulloch,
Tony Northrup,
and Jerry Honeycutt
To learn more about this book, visit Microsoft Learning at
http://www.microsoft.com/MSPress/books/
9780735627000
© 2009 Microsoft Corporation, Tulloch, Northrup, and Honeycutt
Early Content – Subject to Change
Windows 7 Resource Kit
Early Content – Subject to Change
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Table of Contents
Chapter 1 Overview of Windows 7 Architecture
Chapter 2 Security in Windows 7
Chapter 3 Deployment Platform
Chapter 4 Planning Deployment
Chapter 5 Testing Application Compatibility
Chapter 6 Developing Disk Images
Chapter 7 Migrating User State Data
Chapter 8 Deploying Applications
Chapter 9 Preparing Windows PE
Chapter 10 Configuring Windows Deployment Services
Chapter 11 Using Volume Activation
Chapter 12 Deploying with Microsoft Deployment Toolkit
Chapter 13 Overview of Management Tools
Chapter 14 Managing the Desktop Environment
Chapter 15 Managing Users and User Data
Chapter 16 Managing Disks and File Systems
Chapter 17 Managing Devices and Services
Chapter 18 Managing File Sharing
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Chapter 19
Managing Printing
Chapter 20
Managing Search
Chapter 21
Managing Internet Explorer
Chapter 22
Maintaining Desktop Health
Chapter 23
Support Users with Remote Assistance
Chapter 24
Managing Software Updates
Chapter 25
Managing Client Protection
Chapter 26
Configuring Windows Networking
Chapter 27
Configuring Windows Firewall and IPsec
Chapter 28
Connecting Remote Users and Networks
Chapter 29
Deploying IPv6
Chapter 30
Issues
Configuring Startup and Troubleshooting Startup
Chapter 31
Troubleshooting Hardware, Driver, and Disk Issues
Chapter 32
Troubleshooting Network Issues
Chapter 33
Troubleshooting Stop Messages
Appendix A
Accessibility Features in Windows 7
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CHAPTER 29
Deploying IPv6
Like Windows Vista before it, Windows 7 has a new Next Generation TCP/IP stack with
enhanced support for Internet Protocol version 6 (IPv6). This chapter provides you with an
understanding of why IPv6 is necessary and how it works. The chapter describes the IPv6
capabilities in Windows 7, Windows Vista and Windows Server 2008 and outlines how to
migrate the IPv4 network infrastructure of your enterprise to IPv6 using IPv6 transition
technologies such as Intra-Site Automatic Tunnel Addressing Protocol (ISATAP). Finally, the
chapter describes how to configure and manage IPv6 settings in Windows 7 and how to
troubleshoot IPv6 networking problems.
Understanding IPv6
The need for migrating enterprise networks from IPv4 to IPv6 is driven by a number of
different technological, business, and social factors. The most important of these are:

The exponential growth of the Internet is rapidly exhausting the existing IPv4 public
address space. A temporary solution to this problem has been found in Network
Address Translation (NAT), a technology that maps multiple private (intranet)
addresses to a (usually) single, public (Internet) address. Unfortunately, using NATenabled routers can introduce additional problems such as breaking end-to-end
connectivity and security for some network applications. In addition, the rapid
proliferation of mobile IP devices is accelerating the depletion of the IPv4 public
address space.

The growing use of real-time communications (RTC) on the Internet, such as Voice
Over Internet Protocol (VoIP) telephony, Instant Messaging (IM), and audio/video
conferencing, exposes the limited support for Quality of Service (QoS) currently
provided in IPv4. These new RTC technologies need improved QoS on IP networks to
ensure reliable end-to-end communications. The design of IPv4 limits possible
improvements.

The growing threats faced by hosts on IPv4 networks connected to the Internet can
be mitigated considerably by deploying Internet Protocol security (IPsec), both on
private intranets and on tunneled connections across the public Internet. However,
IPsec was designed as an afterthought to IPv4 and is complex and difficult to
implement in many scenarios.
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IPv6, developed by the Internet Engineering Task Force (IETF) to solve these problems,
includes the following improvements and additions:
9

IPv6 increases the theoretical address space of the Internet from 4.3 × 10 addresses
38
(based on 32-bit IPv4 addresses) to 3.4 × 10 possible addresses (based on 128-bit
IPv6 addresses), which most experts agree should be more than sufficient for the
foreseeable future.

The IPv6 address space was designed to be hierarchical rather than flat in structure,
which means that routing tables for IPv6 routers can be smaller and more efficient
than for IPv4 routers.

IPv6 has enhanced support for QoS that includes a Traffic Class field in the header to
specify how traffic should be handled, and a new Flow Label field in the header that
enables routers to identify packets that belong to a traffic flow and handle them
appropriately.

IPv6 now requires IPsec support for standards-based, end-to-end security across the
Internet. The new QoS enhancements work even when IPv6 traffic is encrypted using
IPsec.
Understanding how IPv6 works is essential if you plan to benefit from IPv6 by deploying it
in your enterprise. The following sections provide an overview of key IPv6 concepts, features,
and terminology.
Note For more detailed information on IP concepts, features, and terminology, see
the white paper titled “Introduction to IP Version 6” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=CBC0B8A3-B6A44952-BBE6-D976624C257C&displaylang=en. Another good reference for learning
IPv6 is the book Understanding IPv6, Second Edition, by Joseph Davies (Microsoft
Press, 2008). See http://www.microsoft.com/MSPress/books/11607.aspx.
Understanding IPv6 Terminology
The following terminology is used to define IPv6 concepts and describe IPv6 features:

Node An IPv6-enabled network device that includes both hosts and routers.

Host An IPv6-enabled network device that cannot forward IPv6 packets that are
not explicitly addressed to itself. A host is an endpoint for IPv6 communications
(either the source or destination) and drops all traffic not explicitly addressed to it.

Router An IPv6-enabled network device that can forward IPv6 packets that are not
explicitly addressed to itself. IPv6 routers also typically advertise their presence to
IPv6 hosts on their attached links.

Link One or more LAN (such as Ethernet) or WAN (such as PPP) network segments
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bounded by routers. Like interfaces, links may be either physical or logical.

Neighbors
Nodes that are connected to the same physical or logical link.

Subnet One or more links having the same 64-bit IPv6 address prefix.

Interface A representation of a node‘s attachment to a link. This can be a physical
interface (such as a network adapter) or a logical interface (such as a tunnel
interface).
Note An IPv6 address identifies an interface, not a node. A node is identified by
having one or more unicast IPv6 addresses assigned to one of its interfaces.
Understanding IPv6 Addressing
IPv6 uses 128-bit (16 byte) addresses that are expressed in colon-hexadecimal form. For
example, in the address 2001:DB8:3FA9:0000:0000:0000:00D3:9C5A, each block of 4-digit
hexadecimal numbers represents a 16-bit digit binary number. The eight blocks of four-digit
hexadecimal numbers thus equal 8 × 16 = 128 bits in total.
You can shorten hexadecimal-colon addresses by suppressing leading zeros for each
block. Using this technique, the representation for the preceding address now becomes
2001:DB8:3FA9:0:0:0:D3:9C5A.
You can shorten hexadecimal-colon addresses even further by compressing contiguous 0
(hex) blocks as double colons ("::"). The address in our example thus shortens to
2001:DB8:3FA9::D3:9C5A. Note that only one double colon can be used per IPv6 address to
ensure unambiguous representation.
Understanding IPv6 Prefixes
An IPv6 prefix indicates the portion of the address used for routing (a subnet or a set of
subnets as a summarized route) or for identifying an address range. IPv6 prefixes are
expressed in a similar fashion as the Classless Inter-Domain Routing (CIDR) notation used by
IPv4. For example, 2001:DB8:3FA9::/48 might represent a route prefix in an IPv6 routing table.
In IPv4, CIDR notation can be used to represent individual unicast addresses in addition to
routes and subnets. IPv6 prefixes, however, are used only to represent routes and address
ranges, not unicast addresses. This is because unlike IPv4, IPv6 does not support variable
length subnet identifiers, and the number of high-order bits used to identify a subnet in IPv6
is almost always 64. It is thus redundant to represent the address in our example as
2001:DB8:3FA9::D3:9C5A/64; the /64 portion of the representation is understood.
Understanding IPv6 Address Types
IPv6 supports three different address types:

Unicast Identifies a single interface within the scope of the address. (The scope of
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an IPv6 address is that portion of your network over which this address is unique.)
IPv6 packets with unicast destination addresses are delivered to a single interface.

Multicast Identifies zero or more interfaces. IPv6 packets with multicast destination
addresses are delivered to all interfaces listening on the address. (Generally
speaking, multicasting works the same way in IPv6 as it does in IPv4.)

Anycast Identifies multiple interfaces. IPv6 packets with anycast destination
addresses are delivered to the nearest interface (measured by routing distance)
specified by the address. Currently, anycast addresses are assigned only to routers
and can only represent destination addresses.
Note
IPv6 address types do not include broadcast addresses as used by IPv4. In
IPv6, all broadcast communications are performed using multicast addresses. See
Table 29-2 for more information on multicast addresses.
Understanding Unicast Addresses
Unicast addresses are addresses that identify a single interface. IPv6 has several types of
unicast addresses:
Global Unicast Address An address that is globally routable over the IPv6-enabled
portion of the Internet. Therefore, the scope of a global address is the entire
Internet, and global addresses in IPv6 correspond to public (non-RFC 1918)
addresses used in IPv4. The address prefix currently used for global addresses as
defined in RFC 3587 is 2000::/3, and a global address has the following structure:



The first 48 bits of the address are the global routing prefix specifying your
organization‘s site. (The first three bits of this prefix must be 001 in binary
notation.) These 48 bits represent the public topology portion of the address,
which represents the collection of large and small Internet Service Providers (ISPs)
on the IPv6 Internet, and which is controlled by these ISPs through assignment by
the Internet Assigned Numbers Authority (IANA).

The next 16 bits are the subnet ID. Your organization can use this portion to
specify up to 65,536 unique subnets for routing purposes inside your
organization‘s site. These 16 bits represent the site topology portion of the
address, which your organization has control over.

The final 64 bits are the interface ID and specify a unique interface within each
subnet.
Link-Local Unicast Address An address that can be used by a node for
communicating with neighboring nodes on the same link. Therefore, the scope of a
link-local address is the local link on the network; link-local addresses are never
forwarded beyond the local link by IPv6 routers. Because link-local addresses are
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assigned to interfaces using IPv6 address autoconfiguration, link-local addresses in
IPv6 correspond to Automatic Private IP Addressing (APIPA) addresses used in IPv4
(which are assigned from the address range 169.254.0.0/16). The address prefix used
for link-local addresses is FE80::/64, and a link-local address has the following
structure:

The first 64 bits of the address are always FE80:0:0:0 (which will be shown as
FE80::).

The last 64 bits are the interface ID and specify a unique interface on the local link.
Link-local addresses can be reused—in other words, two interfaces on different links
can have the same address. This makes link-local addresses ambiguous; an additional
identifier called the zone ID (or scope ID) indicates to which link the address is either
assigned or destined. In Windows 7, the zone ID for a link-local address corresponds to
the interface index for that interface. You can view a list of interface indexes on a
computer by typing netsh interface ipv6 show interface at a command prompt. For
more information on the zone ID, see the section titled ―Displaying IPv6 Address
Settings‖ later in this chapter.

Note
Unique Local Unicast Address Because a site-local address prefix can represent
multiple sites within an organization, it is ambiguous and not well-suited for
intraorganizational routing purposes. Therefore, RFC 4193 currently proposes a new
type of address called a unique local unicast address. The scope of this address is
global to all sites within the organization, and using this address type simplifies the
configuration of an organization‘s internal IPv6 routing infrastructure. A unique local
address has the following structure:

The first seven bits of the address are always 1111 110 (binary) and the eighth
bit is set to 1, indicating a unique local address. This means that the address
prefix is always FD00::/8 for this type of address.

The next 40 bits represent the global ID, a randomly generated value that
identifies a specific site within your organization.

The next 16 bits represent the subnet ID and can be used for further subdividing
the internal network of your site for routing purposes.

The last 64 bits are the interface ID and specify a unique interface within each
subnet.
Site-local addresses have been deprecated by RFC 3879 and are replaced by
unique local addresses.
Identifying IPv6 Address Types
As Table 29-1 shows, you can quickly determine which type of IPv6 address you are dealing
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with by looking at the beginning part of the address—that is, the high-order bits of the
address. Tables 29-2 and 29-3 also show examples of common IPv6 addresses that you can
recognize directly from their colon-hexadecimal representation.
Table 29-1 Identifying IPv6 Address Types Using High-Order Bits and Address Prefix
ADDRESS TYPE
HIGH-ORDER BITS
ADDRESS PREFIX
Global unicast
001
2000::/3
Link-local unicast
1111 1110 10
FE80::/64
Unique local unicast
1111 1101
FD00::/8
Multicast
1111 1111
FF00::/8
Table 29-2 Identifying Common IPv6 Multicast Addresses
FUNCTION
SCOPE
REPRESENTATION
All-nodes multicast
Interface-local
FF01::1
All-nodes multicast
Link-local
FF02::1
All-routers multicast
Interface-local
FF01::2
All-routers multicast
Link-local
FF02::2
All-routers multicast
Site-local
FF05::2
Table 29-3 Identifying Loopback and Unspecified IPv6 Addresses
FUNCTION
REPRESENTATION
Unspecified address (no address)
::
Loopback address
::1
Note
For information on IPv6 address types used by different IPv6 transition
technologies, see the section titled “Planning for IPv6 Migration” later in this
chapter.
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Understanding Interface Identifiers
For all the types of unicast IPv6 addresses described in the preceding sections, the last 64 bits
of the address represent the interface ID and are used to specify a unique interface on a local
link or subnet. In previous versions of Windows, the interface ID is uniquely determined as
follows:

For link-local addresses, such as a network adapter on an Ethernet segment, the
interface ID is derived from either the unique 48-bit MAC-layer (Media Access
Control) address of the interface or the unique EUI-64 (Extended Unique Identifier)
address of the interface as defined by the Institute of Electrical and Electronics
Engineers (IEEE).

For global address prefixes, an EIU-64–based interface ID creates a public IPv6
address.

For global address prefixes, a temporary random interface ID creates a temporary
address. This approach is described in RFC 3041; you can use it to help provide
anonymity for client-based usage of the IPv6 Internet.
In Windows 7, however, the interface ID by default is randomly generated for all types of
unicast IPv6 addresses assigned to LAN interfaces.
Note Windows 7 randomly generates the interface ID by default. You can also
disable this behavior by typing netsh interface ipv6 set global
randomizedidentifiers=disabled at a command prompt.
Comparing IPv6 with IPv4
Table 29-4 compares and contrasts the IPv4 and IPv6 addressing schemes.
Table 29-4 IPv4 vs. IPv6 Addressing
FEATURE
IPv4
IPv6
Number of bits (bytes)
32 (4)
128 (16)
Expressed form
Dotted-decimal
Colon-hexadecimal
Variable-length subnets
Yes
No
Public addresses
Yes
Yes (global addresses)
Private addresses
Yes (RFC 1918 addresses)
Yes (unique local
addresses)
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Autoconfigured addresses
for the local link
Yes (APIPA)
Yes (link-local addresses)
Support for address classes
Yes, but deprecated by CIDR
No
Broadcast addresses
Yes
Multicast used instead
Subnet mask
Required
Implicit 64-bit address
prefix length for addresses
assigned to interfaces
Note
For detailed specifications concerning IPv6 addressing, see RFC 4291 at
http://www.ietf.org/rfc/rfc4291.txt. There are also other differences between IPv4
and IPv6, such as how the headers are structured for IPv4 versus IPv6 packets. For
more information, see the white paper “Introduction to IP Version 6” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=CBC0B8A3-B6A44952-BBE6-D976624C257C&displaylang=en.
Understanding IPv6 Routing
Routing is the process of forwarding packets between connected network segments and is
the primary function of IPv6. An IPv6 network consists of one or more network segments, also
called links or subnets. These links are connected together by IPv6 routers, devices that
forward IPv6 packets from one link to another. These IPv6 routers are typically third-party
hardware devices, but you can also configure a multihomed Windows Server 2008 computer
as an IPv6 router if needed.
How IPv6 Routing Works
The header of an IPv6 packet contains both the source address of the sending host and the
destination address of the receiving host. When an IPv6 packet arrives at a host, the host uses
its local IPv6 routing table to determine whether to accept the packet or forward it to another
host or network.
Each IPv6 node (host or router) has its own IPv6 routing table. A routing table is a
collection of routes that store information about IPv6 network prefixes and how they can be
reached, either directly or indirectly. On IPv6 hosts such as computers running Windows 7,
Windows Vista, or Windows Server 2008, the IPv6 routing table is generated automatically
when IPv6 initializes on the system. Local administrators can use the netsh interface ipv6
commands to manage these tables by viewing them and by manually adding or removing
routes. Use of this command is discussed further below.
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When an IPv6 packet arrives at a physical or logical network interface on an IPv6 host such
as a multihomed Windows Server 2008 computer, the host uses the following process to
determine how to forward the packet to its intended destination:
1.
The host checks its destination cache to see if there is an entry that matches the
destination address in the packet header. If such an entry is found, the host forwards
the packet directly to address specified in the destination cache entry and the routing
process ends.
2.
If the destination cache does not contain an entry that matches the destination address
in the packet header, the host uses its local routing table to determine how to forward
the packet. Using the routing table, the host determines:
3.

Next-hop address If the destination address is on the local link, the next-hop
address is simply the destination address in the packet header. If the destination
address is on a remote link, the next-hop address is the address of a router
connected to the local link.

Next-hop interface This is the physical or logical network interface on the host
that should be used to forward the packet to the next-hop address.
The host then forwards the packet to the next-hop address using the next-hop
interface. The host also updates its destination cache with this information so that
subsequent packets sent to the same destination address can be forwarded using the
destination cache entry instead of having to use its local routing table.
IPv6 Route Determination Process
In step 2 above, the host determines the next-hop address and next-hop interface by using its
local routing table. The details of this process are as follows:
1.
For each routing table entry, the first N bits in the route's network prefix are compared
with the same bits in the destination address in the packet header, where N is the
number of bits in the route's prefix length. If these bits match, the route is determined
to be a match for the destination.
2.
The list of all matching routes is compiled. If only one matching route is found, this
route is chosen and the route determination process is ended.
3.
If multiple matching routes are found, the matching route having the largest prefix
length is chosen and the route determination process is ended.
4.
If multiple matching routes having the largest prefix length are found, the matching
route having the lowest metric is chosen and the route determination process is
ended.
5.
If multiple matching routes having the largest prefix length and lowest metric are
found, one of these routes is selected and the route determination process is ended.
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The effective result of the above IPv6 route determination process is as follows:
1.
If a route can be found that matches the entire destination address in the packet
header, then the next-hop address and interface specified in this route are used to
forward the packet.
2.
If the above is not found, the most efficient (lowest metric) route that has the longest
prefix length matching the destination address is used to forward the packet.
3.
If neither of the above are found, the packet is forwarded using the default route
(network prefix ::/0).
IPv6 Routing Table Structure
IPv6 routing tables can contain four different types of routing table entries (routes):

Directly-attached network routes These typically have 64-bit prefixes and identify
adjacent links (network segments connected to the local segment via one router).

Remote network routes These have varying prefixes and identify remote links
(network segments connected to the local segment via several routers).

Host routes

Default route This uses the prefix ::/0 and is used to forward packets when a
network or host route cannot be determined.
These have 128-bit prefixes and identify a specific IPv6 node.
On a Windows 7, Windows Vista, or Windows Server 2008 computer, you can use the
netsh interface ipv6 show route command to display the IPv6 routing table entries. The
following is a sample routing table from a domain-joined Windows 7 computer that has
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a single LAN network adapter and where there are no IPv6 routers on the attached subnet
and no other configured network connections:
Publish
Type
Met
Prefix
Idx
-------
--------
---
------------------------
---
No
Manual
256
::1/128
No
Manual
256
fe80::/64
15
Teredo Tunneling Pseudo-Interface
No
Manual
256
fe80::/64
12
Local Area Connection
No
Manual
256
fe80::100:7f:fffe/128
15
Teredo Tunneling Pseudo-Interface
No
Manual
256
fe80::5efe:172.16.11.131/128
1
Gateway/Interface Name
-----------------------Loopback Pseudo-Interface 1
14
isatap.{9D607D7D-0703-4E67-
82ED-9A8206377C5C}
No
Manual
256
fe80::5da9:fa1d:2575:c766/128
No
Manual
256
ff00::/8
1
12
Local Area Connection
No
Manual
256
ff00::/8
15
Teredo Tunneling Pseudo-Interface
No
Manual
256
ff00::/8
12
Local Area Connection
Loopback Pseudo-Interface 1
Each route in this table is specified using the following fields:

Publish If Yes, the route is advertised in a routing Advertisement message;
otherwise No.

Type If Autoconf, the route was configured automatically using the IPv6 routing
protocol; if Manual, the route has been configured by the operating system or an
application.

Met Indicates the metric for the route. For multiple routes having the same prefix,
the lower the metric, the better the match.

Prefix Specifies the address prefix for the route.

Idx Specifies the index of the network interface over which packets matching the
route's address prefix are reachable. To display a list of interfaces and their indices,
use the netsh interface ipv6 show interface command.

Gateway/Interface Name For directly-attached network routes, specifies the name
of the interface; for remote network routes, specifies the next-hop address of the
route.
Note
For more information about IPv6 routing and routing tables, see the Cable
Guy article titled "”Understanding the IPv6 Routing Table” at
http://technet.microsoft.com/en-ca/library/bb878115.aspx.
Understanding ICMPv6 Messages
Internet Control Message Protocol (ICMP) for IPv4 (ICMPv4) is used in IPv4 networks to allow
nodes to send and respond to error messages and informational messages. For example,
when a source node uses the ping command to send ICMP Echo Request messages (ICMP
type 8 messages) to a destination node, the destination node can respond with ICMP Echo
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messages (ICMP type 0 messages) indicating its presence on the network.
On IPv6 networks, ICMP for IPv6 (ICMPv6) fulfills the same functions that ICMPv4 does on
IPv4 networks—namely, to provide a mechanism for exchanging error messages and
informational messages. ICMPv6 also provides information messages for the following:

Neighbor Discovery (ND) The process by which hosts and routers discover each
other on the network so that they can communicate at the data-link layer. (Network
Discovery serves the same purpose as ARP does in IPv4 networks.)

Multicast Listener Discovery (MLD) The process by which membership in multicast
groups is determined and maintained.
Note
For more information about Neighbor Discovery, see the section titled
“Understanding Neighbor Discovery” later in this chapter. For more information
about ICMPv6 message types and header formats, and about Multicast Listener
Discovery, see the white paper “Introduction to IP Version 6” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=CBC0B8A3-B6A44952-BBE6-D976624C257C&displaylang=en.
Understanding Neighbor Discovery
Neighbor Discovery (ND) is the process by which nodes on an IPv6 network can communicate
with each other by exchanging frames at the data-link layer. ND performs the following
functions on an IPv6 network:

Enables IPv6 nodes (IPv6 hosts and IPv6 routers) to resolve the link-layer address of
a neighboring node (a node on the same physical or logical link)

Enables IPv6 nodes to determine when the link-layer address of a neighboring node
has changed

Enables IPv6 nodes to determine whether neighboring nodes are still reachable

Enables IPv6 routers to advertise their presence, on-link prefixes, and host
configuration settings

Enables IPv6 routers to redirect hosts to more optimal routers for a specific
destination

Enables IPv6 hosts to discover addresses, address prefixes, and other configuration
settings

Enables IPv6 hosts to discover routers attached to the local link
To understand how ND works, it helps to first compare it with the similar processes used in
IPv4. In IPv4, you use three separate mechanisms to manage node-to-node communication:

Address Resolution Protocol (ARP) A data-link layer protocol that resolves IPv4
addresses assigned to interfaces to their corresponding MAC-layer addresses. This
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enables network adapters to receive frames addressed to them and send response
frames to their source. For example, before a host can send a packet to a destination
host whose IPv4 address is 172.16.25.3, the sending host first needs to use ARP to
resolve this destination address (if the host is on the same LAN) or the IP address of
the local gateway (if the host is on a different LAN) to its corresponding 48-bit MAC
address (such as 00-13-20-08-A0-D1).

ICMPv4 Router Discovery These ICMPv4 messages enable routers to advertise their
presence on IPv4 networks and enable hosts to discover the presence of these
routers. When Router Discovery is enabled on a router, the router periodically sends
Router Advertisements to the all-hosts multicast address (224.0.0.1) to indicate to
hosts on the network that the router is available. When Router Discovery is enabled
on hosts, the hosts can send Router Solicitations to the all-routers multicast address
(224.0.0.2) to obtain the address of the router and assign this address as the host‘s
default gateway.

ICMPv4 Redirect Routers use these ICMPv4 messages to inform hosts of more
optimal routers to use for specific destinations. ICMPv4 Redirect messages are
needed because hosts typically cannot determine the best router on their subnet to
send remote traffic for a given destination.
On IPv4 networks, these three mechanisms enable nodes on a network segment to
communicate on a link. On IPv6 networks, these three mechanisms are replaced by the five
ICMPv6 message types shown in Table 29-5.
Table 29-5 ICMPv6 Message Types Used for Neighbor Discovery
MESSAGE TYPE
ICMPV6 TYPE
DESCRIPTION
Router Solicitation
133
Sent by IPv6 hosts to the link-local scope all-routers
multicast address (FF02::2) to discover IPv6 routers
present on the local link.
Router
Advertisement
134
Sent periodically by IPv6 routers to the link-local scope
all-nodes multicast address (FF02::1), or sent to the
unicast address of a host in response to receiving a
Router Solicitation message from that host. (Windows
Vista and later use multicast for optimization.) Router
Advertisement messages provide hosts with the
information needed to determine link prefixes, link
MTU, whether or not to use DHCPv6 for address
autoconfiguration, and lifetime for autoconfigured
addresses.
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Neighbor
Solicitation
135
Sent by IPv6 nodes to the solicited-node multicast
address of a host to discover the link-layer address of
an IPv6 node, or sent to the unicast address of the host
to verify the reachability of the host.
Neighbor
Advertisement
136
Sent by an IPv6 node to the unicast address of a host
in response to receiving a Neighbor Solicitation
message from the host, or sent to the link-local scope
all-nodes multicast address (FF02::1) to inform
neighboring nodes of changes to the host‘s link-layer
addresses.
Redirect
137
Sent by an IPv6 router to the unicast address of a host
to inform the host of a more optimal first-hop address
for a specific destination.
Note The solicited-node multicast address, which is used as the destination
address for ICMPv4 Neighbor Solicitation messages (ICMPv6 type 135 messages)
when address resolution is being performed, is a special type of multicast address
composed of the prefix FF02::1:FF00:0/104 followed by the last 24 bits of the IPv6
address that is being resolved. IPv6 nodes listen on their solicited-node multicast
addresses. The advantage of using this multicast address for address resolution in
IPv6 is that typically only the targeted host is disturbed on the local link. By
contrast, the ARP messages used in IPv4 for address resolution queries are sent to
the MAC-layer broadcast address, which disturbs all hosts on the local segment.
Understanding Address Autoconfiguration
On IPv4 networks, addresses can be assigned to hosts in three ways:

Manually using static address assignment

Automatically using DHCP, if a DHCP server is present on the subnet (or a DHCP
relay agent configured on the subnet)

Automatically using Automatic Private IP Addressing (APIPA), which randomly
assigns the host an address from the range 169.254.0.0 to 169.254.255.255 with
subnet mask 255.255.0.0
On IPv6 networks, static addresses are generally assigned only to routers and sometimes
servers, but hardly ever to client computers. Instead, IPv6 addresses are almost always
assigned automatically using a process called address autoconfiguration. Address
autoconfiguration can work in three ways: stateless, stateful, or both. Stateless address
autoconfiguration is based on the receipt of ICMPv6 Router Advertisement messages. Stateful
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address autoconfiguration, on the other hand, uses DHCPv6 to obtain address information
and other configuration settings from a DHCPv6 server.
Note The DHCP Server service of Windows Server 2008 supports DHCPv6. The
DHCP Server service of Windows Server 2003 does not support DHCPv6.
All IPv6 nodes (hosts and routers) automatically assign themselves link-local addresses
(addresses having the address prefix FE80::/64); this is done for every interface (both physical
and logical) on the node. (6to4 interfaces are an exception—they might not have link-local
addresses automatically assigned.) These autoconfigured link-local addresses can be used
only to reach neighboring nodes (nodes on the same link). When specifying one of these
addresses as a destination address, you might need to specify the zone ID for the destination.
In addition, link-local addresses are never registered in DNS servers.
Note
Manual assignment of IPv6 addresses is generally needed only for IPv6
routers and for some servers. You can configure a Windows 7 computer with
multiple interfaces to be used as a router. For more information on configuring IPv6
routers, see the Cable Guy article titled “Manual Configuration for IPv6” at
http://technet.microsoft.com/en-us/library/bb878102.aspx. For a description of
the IPv6 routing table, see the Cable Guy article titled “Understanding the IPv6
Routing Table” at http://technet.microsoft.com/en-us/library/bb878115.aspx.
An autoconfigured IPv6 address can be in one or more of the states shown in Table 29-6.
Table 29-6 Possible States for an Autoconfigured IPv6 Address
STATE
DESCRIPTION
Tentative
The uniqueness of the address is still being verified using duplicate address
detection.
Valid
The address is unique and can now send and receive unicast IPv6 traffic until
the Valid Lifetime expires.
Preferred
The address can be used for unicast traffic until the Preferred Lifetime
expires.
Deprecated
The address can still be used for unicast traffic during existing
communication sessions, but its use is discouraged for new communication
sessions.
Invalid
The Valid Lifetime for the address has expired and it can no longer be used
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for unicast traffic.
Note The Valid and Preferred lifetime for stateless autoconfigured IPv6 addresses
is included in the Router Solicitation message.
For detailed descriptions of how address autoconfiguration, address resolution, router
discovery, redirect, duplicate address detection, and neighbor unreachability detection
processes are performed, see the white paper ―Introduction to IP Version 6‖ at
http://www.microsoft.com/downloads/details.aspx?FamilyID=CBC0B8A3-B6A4-4952-BBE6D976624C257C&displaylang=en.
Note To display the state for each autoconfigured IPv6 address on a Windows 7
computer, open a command prompt and type netsh interface ipv6 show addresses
at a command prompt.
Understanding Name Resolution
The Domain Name System (DNS) is fundamental to how name resolution works on both IPv4
and IPv6 networks. On an IPv4 network, host (A) records are used by name servers (DNS
servers) to resolve fully qualified domain names (FQDNs) like server1.contoso.com into their
associated IP addresses in response to name lookups (name queries) from DNS clients. In
addition, reverse lookups—in which IP addresses are resolved into FQDNs—are supported by
using pointer (PTR) records in the in-addr.arpa domain.
Name resolution works fundamentally the same way with IPv6, with the following
differences:

Host records for IPv6 hosts are AAAA (―quad-A‖) records, not A records.

The domain used for reverse lookups of IPv6 addresses is ip6.arpa, not in-addr.arpa.
Note The enhancements to the Domain Name System that make IPv6 support
possible are described in the draft standard RFC 3596 at
http://www.ietf.org/rfc/rfc3596.txt.
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Understanding Name Queries
Because the dual-layer TCP/IP stack in Windows 7 means that both IPv4 and IPv6 are enabled
by default, DNS name lookups by Windows 7 client computers can involve the use of both A
and AAAA records. (This is true only if your name servers support IPv6, which is the case with
the DNS Server role for Windows Server 2008 and Windows Server 2003.) By default, the DNS
client component in Windows 7 uses the following procedure when performing a name
lookup using a particular interface:
1.
The client computer checks to see whether it has a non-link-local IPv6 address
assigned to the interface. If it has no non-link-local addresses assigned, the client
sends a single name lookup to the name server to query for A records and does not
query for AAAA records. If the only non-link-local address assigned to the interface is a
Teredo address, the client again does not query for AAAA records. (The Teredo client in
Windows Vista and later has been explicitly built not to automatically perform AAAA
lookups or register with DNS to prevent overloading of DNS servers.)
2.
If the client computer has a non-link-local address assigned to the interface, the client
sends a name lookup to query for A records.

If the client then receives a response to its query (not an error message), it follows
with a second lookup to query for AAAA records.

If the client receives no response or receives any error message (except for Name
Not Found), it does not send a second lookup to query for AAAA records.
Note Because an interface on an IPv6 host typically has multiple IPv6 addresses,
the process by which source and address selection works during a name query is
more complex than when DNS names are resolved by IPv4 hosts. For a detailed
description of how source and address selection works for IPv6 hosts, see the Cable
Guy article titled “Source and Destination Address Selection for IPv6” at
http://technet.microsoft.com/en-us/library/bb877985.aspx. For additional
information on DNS behavior in Windows 7 and Windows Vista, see “Domain Name
System Client Behavior in Windows Vista” at http://technet.microsoft.com/en-
us/library/bb727035.aspx. For information about the different types of IPv6
addresses usually assigned to an interface, see the section titled “Configuring and
Troubleshooting IPv6 in Windows Vista” later in this chapter.
Note
Issues have arisen with poorly configured DNS name servers on the Internet.
These issues, which are described in RFC 4074
(http://www.ietf.org/rfc/rfc4074.txt), do not cause problems on Windows Vista or
later because Microsoft has altered the DNS client behavior specifically to
compensate for them. However, administrators of DNS servers should make sure
these issues are fixed, because they can cause problems with DNS name resolution
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for most IPv6 networking stacks, including stacks found in legacy Windows
platforms such as Windows XP.
Understanding Name Registration
DNS servers running Windows Server 2003 can dynamically register both A and AAAA records
for Windows 7 client computers. Dynamic registration of DNS records simplifies the job of
maintaining name resolution on networks running the Active Directory directory service.
When a Windows 7 client computer starts up on a network, the DNS Client service tries to
register the following records for the client:

A records for all IPv4 addresses assigned to all interfaces configured with the address
of a DNS server

AAAA records for all IPv6 addresses assigned to all interfaces configured with the
address of a DNS server

PTR records for all IPv4 addresses assigned to all interfaces configured with the
address of a DNS server
Note
AAAA records are not registered for link-local IPv6 addresses that have been
assigned to interfaces using address autoconfiguration.
PTR Records and IPv6
Windows 7 client computers do not try to register PTR records for IPv6 addresses
assigned to interfaces on the computer. If you want to enable clients to perform
reverse lookups for Windows 7 computers using IPv6, you must manually create a
reverse lookup zone for the ip6.arpa domain on your DNS servers and then manually
add PTR records to this zone. For detailed steps on how to do this, see “IPv6 for
MicrosoftWindows: Frequently Asked Questions” at
http://www.microsoft.com/technet/network/ipv6/ipv6faq.mspx.
However, PTR records for reverse lookups using IPv6 are not often used, because
the namespace for reverse queries is formed by using each hexadecimal digit in the
colon-hexadecimal representation of an IPv6 address as a separate level in the
reverse domain hierarchy. For example, the PTR record associated with the IPv6
address 2001:DB8::D3:00FF:FE28:9C5A, whose full representation is
2001:0DB8:0000:0000:00D3:00FF:FE28:9C5A, would be expressed as
A.5.C.9.8.2.E.F.F.F.0.0.3.D.0.0.0.0.0.0.0.0.0.0.8.B.D.0.1.0.0.2.IP6.ARPA. The
performance cost of resolving such a representation would generally be too high for
most DNS server implementations.
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By default, DNS servers running Windows Server 2003 do not listen for DNS traffic sent
over IPv6. To enable these DNS servers to listen for IPv6 name registrations and name
lookups, you must first configure the servers using the dnscmd /config /EnableIPv6 1
command. By default, DNS servers running Windows Server 2008 listen for DNS traffic sent
over IPv6. You must then configure each Windows 7 client computer with the unicast IPv6
addresses of your DNS servers using DHCPv6, the properties of the Internet Protocol Version
6 (TCP/IPv6) component in the Network Connections folder, or the netsh interface ipv6 add
dns interface=NameOrIndex address=IPv6Address index=PreferenceLevel command.
(DHCP servers running Windows Server 2003 do not support stateful address assignment
using DHCPv6.)
Note
For more information on enabling Windows Server 2003 DNS server support
for IPv6, see Chapter 9, “Windows Support for DNS” in the online book TCP/IP
Fundamentals for Microsoft Windows, which you can download from
http://www.microsoft.com/downloads/details.aspx?FamilyID=c76296fd-61c94079-a0bb-582bca4a846f &displaylang=en. For further details on the DNS name
query and registration behavior in Windows 7 and Windows Vista, see the article
titled “Domain Name System Client Behavior in Windows Vista” on Microsoft
TechNet at http://technet.microsoft.com/en-us/library/bb727035.aspx.
IPv6 Enhancements in Windows 7
The TCP/IP networking stack in the Windows XP and Windows Server 2003 platforms had a
dual-stack architecture that used separate network and framing layers for IPv4 and IPv6 based
on separate drivers: Tcpip.sys and Tcpip6.sys. Only the transport and framing layers for IPv4
were installed by default, and adding support for IPv6 involved installing an additional IPv6
protocol component through the Network Connections folder.
By contrast, in Windows 7, Windows Vista and Windows Server 2008, the TCP/IP stack has
been completely redesigned and now uses a dual IP layer architecture in which both IPv4 and
IPv6 share common transport and framing layers. In addition, IPv6 is installed and enabled by
default in these new platforms to provide out-of-the-box support for new features such as
the Windows Meeting Space application, which uses only IPv6. Finally, the dual IP layer
architecture means that all of the performance enhancements of the Next Generation TCP/IP
stack that apply to IPv4 also apply to IPv6. These performance enhancements include
Compound TCP, Receive Window Auto-Tuning, and other enhancements that can
dramatically improve performance in high-latency, high-delay, and high-loss networking
environments.
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Note For more information about the performance enhancements in the Next
Generation TCP/IP stack, see Chapter 26, “Configuring Windows Networking.”
Summary of IPv6 Enhancements in Windows 7
Windows 7 builds upon the many IPv6 enhancements introduced earlier in Windows Vista and
Windows Server 2008. These earlier enhancements included:

Dual IP layer architecture A new TCP/IP stack architecture that uses the same
transport and framing layers for both IPv4 and IPv6.

Enabled by default Both IPv4 and IPv6 are installed and enabled by default, with
the stack giving preference to IPv6 when appropriate without impairing the
performance of IPv4 communications on the network. For example, if a DNS name
query returns both an IPv4 and IPv6 address for a host, the client will try to use IPv6
first for communicating with the host. This preference also results in better network
performance for IPv6-enabled applications.

User interface configuration support In addition to being able to configure IPv6
settings from the command line using the netsh interface ipv6 command context,
you can also configure them in Windows 7 using the user interface. For more
information, see the section titled ―Configuring IPv6 in Windows 7 Using the User
Interface‖ later in this chapter.

Full IPsec support IPv6 support in previous versions of Windows offered only
limited support for IPsec protection of network traffic. In Windows 7 and Windows
Vista, however, IPsec support for IPv6 is the same as for IPv4, and you can configure
IPsec connection security rules for IPv6 the same as for IPv4, using the Windows
Firewall With Advanced Security console. For more information on configuring IPsec
in Windows 7, see Chapter 27, ―Configuring Windows Firewall and IPsec.‖

LLMNR support The implementation of IPv6 in Windows 7 and Windows Vista
supports Link-Local Multicast Name Resolution (LLMNR), a mechanism that enables
IPv6 nodes on a single subnet to resolve each other‘s names in the absence of a DNS
server. LLMNR works by having nodes send multicast DNS name queries instead of
unicast queries. Windows 7 and Windows Vista computers listen by default for
multicast LLMNR traffic, which eliminates the need to perform local subnet name
resolution using NetBIOS over TCP/IP when no DNS server is available. LLMNR is
defined in RFC 4795.

MLDv2 support The implementation of IPv6 in Windows 7 and Windows Vista
supports Multicast Listener Discovery (MLD) version 2 (MLDv2), a mechanism
described in RFC 3810 that enables IPv6 hosts to register interest in source-specific
multicast traffic with local multicast routers by specifying an include list (to indicate
specific source addresses of interest) or an exclude list (to exclude unwanted source
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addresses).

DHCPv6 support The DHCP Client service in Windows 7 and Windows Vista
supports Dynamic Host Configuration Protocol for IPv6 (DHCPv6) as defined in RFCs
3736 and 4361. This means that Windows 7 and Windows Vista computers can
perform both stateful and stateless DHCPv6 configuration on a native IPv6 network.

IPV6CP support The built-in remote access client component in Windows 7 and
Windows Vista supports IPv6 Control Protocol (IPV6CP) (RFC 5072) to configure IPv6
nodes on a Point-to-Point Protocol (PPP) link. This means that native IPv6 traffic can
be sent over PPP-based network connections such as dial-up connections or
broadband PPP over Ethernet (PPPoE) connections to an Internet Service Provider
(ISP). IPV6CP also supports Layer 2 Tunneling Protocol (L2TP), and for Windows Vista
with Service Pack 1 or later, Secure Socket Tunneling Protocol (SSTP)–based Virtual
Private Network (VPN) connections. For more information on IPV6CP support in
Windows 7, see Chapter 28, ―Connecting Remote Users and Networks.‖

Random interface IDs By default, Windows 7 and Windows Vista generate random
interface IDs for nontemporary autoconfigured IPv6 addresses, including both public
addresses (global addresses registered in DNS) and link-local addresses. For more
information, see the section titled ―Disabling Random Interface IDs‖ later in this
chapter.

Literal IPv6 addresses in URLs Windows 7 and Windows Vista support RFC 2732–
compliant literal IPv6 addresses in URLs by using the new WinINet API support in
Microsoft Internet Explorer 7.0. This can be a useful feature for troubleshooting
Internet connectivity with IPv6-enabled Web servers.

New Teredo Behavior The Teredo client in Windows 7 and Windows Vista remains
dormant (inactive) until it spins up (is activated by) an IPv6-enabled application that
tries to use Teredo. In Windows 7 and Windows Vista, three things can bring up
Teredo: an application trying to communicate using a Teredo address (the outbound
instantiated scenario); a listening application that has the Edge Traversal rule
enabled in Windows Firewall (any IPv6-enabled applications that need to use Teredo
can easily do so by setting the Edge Traversal flag using the Windows Firewall APIs);
and the NotifyStableUnicastIpAddressTable IP Helper API. For more information
about Windows Firewall rules, see Chapter 27.
In addition to these earlier enhancements, Windows 7 and Windows Server 2008 R2
introduce the following new IPv6 enhancements:

IP-HTTPS This stands for Internet Protocol over Secure Hypertext Transfer Protocol
(IP over HTTPS), a new protocol that enables hosts located behind a proxy or firewall
to establish connectivity by tunneling IP traffic inside an HTTPS tunnel. HTTPS is used
instead of HTTP so that proxy servers will be prevented from looking inside the data
stream and terminate the connection if traffic seems anomalous. Note that HTTPS
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does not providing data security—you must use IPsec to provide data security for an
IP-HTTPS connection.
In the Windows 7 implementation of DirectAccess described below, IT-HTTPS is used
whenever a firewall or proxy server blocks a client computer from using 6to4 or Teredo
to establish an IPv6-over-IPv4 tunnel with an IPv6-enabled DirectAccess server on the
corporate intranet.
For more information about IP-HTTPS, see the IP over HTTPS (IP-HTTPS) Tunneling
Protocol Specification on MSDN at http://msdn.microsoft.com/enus/library/dd358571(PROT.10).aspx.

DirectAccess This is a new feature of Windows 7 and Windows Server 2008 R2 that
provides users with the experience of being seamlessly connected to the corporate
network whenever they have Internet access. Using DirectAccess, remote users who
attempt to access corporate intranet resources such as e-mail servers, shared folders,
or intranet Web sites can access these resources without the need of having to
connect to a virtual private network (VPN). By providing users with the same
connectivity experience both inside and outside of the office, DirectAccess can
increase the productivity of your mobile users. DirectAccess also enables
administrators to keep the computers of mobile uses in a managed state even when
they are off-site by allowing Group Policy changes to be propagated over the
Internet.
DirectAccess is implemented as a client/server architecture in which remote IPv6enabled client computers communicate with IPv6-enabled servers located on the
corporate network. DirectAccess can work over existing IPv4 networks such as the
public IPv4 Internet by leveraging IPv4/v6 transition technologies such as 6to4, Teredo
and ISATAP. DirectAccess also supports native IPv6 connectivity for clients that have
been assigned native IPv6 addresses.
DirectAccess uses IPsec tunneling to provide security for authentication and resource
access. DirectAccess can be implemented in different ways ranging from providing
client computers with secure access to intranet resources via an IPv6-enabled IPsec
gateway to providing them with secure end-to-end connectivity with each IPv6enabled application server located on the intranet. DirectAccess requires the use of
IPv6 so that client computers can have globally-routable addresses.
For more information about DirectAccess, see Chapter 26 Configuring Windows
Networking in this Resource Kit. Also see the Technical Overview of DirectAccess in
Windows 7 and Windows Server 2008 R2, which can be obtained from the Microsoft
Download Center at http://www.microsoft.com/downloads/.
How It Works: Teredo Behavior in Windows 7 and Windows Vista
Teredo is default-enabled but inactive in both workgroup and domain scenarios.
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Teredo becomes active in two main scenarios:
 An application tries to communicate with a Teredo address (for example, by using a URL
with a Teredo address in a Web browser). This is outbound-initiated traffic, and Teredo
will go dormant again after 60 minutes of inactivity. The host firewall will allow only
incoming Teredo traffic corresponding to the specific outbound request, ensuring that
system security isn’t compromised. This is really no different than how any outboundinitiated traffic works with the host firewall with IPv4. (In other words, all outbound
traffic is allowed by default, and a state table allows responses that match the outgoing
requests.)
 An application or service is authorized to use Teredo with the advanced Windows
Firewall Edge Traversal flag. If an application has the Edge Traversal option, it is
allowed to receive any incoming traffic over Teredo from any source (such as
unsolicited traffic). Windows Meeting Space and Remote Assistance automatically set
this flag for themselves, but users can do it manually for other Windows services if they
prefer, such as with a web service.
Michael Surkan
Program Manager for TCP and IPv6
Configuring and Troubleshooting IPv6 in Windows 7
Although IPv6 is designed to allow IPv6-enabled nodes such as Windows 7 computers to
automatically configure their interfaces with link-local addresses, these autoconfigured
addresses are not registered in DNS servers and can be used only for communicating with
other nodes on the local link. Alternatively, by using a DHCPv6 server, you can automatically
assign global, site-local, or unique local IPv6 addresses to IPv6-enabled interfaces of linkattached nodes. This is the preferred scenario for end-to-end IPv6 connectivity in enterprises
that have a native IPv6-only network infrastructure.
However, you can also use two methods to configure IPv6 settings manually on Windows 7
computers:

Using the new IPv6 graphical user interface

Using the netsh interface ipv6 command context
In addition, it is important to understand the different kinds of IPv6 addresses assigned to
Windows 7 computers so that you can troubleshoot IPv6 connectivity when problems arise.
Displaying IPv6 Address Settings
To display the IPv4 and IPv6 address configuration of the local computer, open a command
prompt window and type ipconfig /all at a command prompt. The following is an example of
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the information displayed by running this command on a domain-joined Windows 7
computer with a single LAN network adapter, no IPv6 routers on the attached subnet, and no
other configured network connections:
Windows IP Configuration
Host Name . . . . . . . . . . . . : KBERG-PC
Primary Dns Suffix
. . . . . . . : contoso.com
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix
. : contoso.com
Description . . . . . . . . . . . : Broadcom NetXtreme 57xx Gigabit Controller
Physical Address. . . . . . . . . : 00-13-D4-C2-50-F5
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::3530:6107:45a2:a92c%8(Preferred)
IPv4 Address. . . . . . . . . . . : 172.16.11.13(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Tuesday, March 17, 2009 9:01:24 AM
Lease Expires . . . . . . . . . . : Wednesday, March 25, 2009 9:01:29 AM
Default Gateway . . . . . . . . . : 172.16.11.1
DHCP Server . . . . . . . . . . . : 172.16.11.32
DHCPv6 IAID . . . . . . . . . . . : 201331668
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-11-50-8C-A7-00-17-31-C5-D2-8E
DNS Servers . . . . . . . . . . . : 172.16.11.32
NetBIOS over Tcpip. . . . . . . . : Enabled
Tunnel adapter isatap.{9D607D7D-0703-4E67-82ED-9A8206377C5C}:
Media State . . . . . . . . . . . : Enabled
Connection-specific DNS Suffix
. :
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::5efe:172.16.11.13%9(Preferred)
Default Gateway . . . . . . . . . :
DNS Servers . . . . . . . . . . . : 172.16.11.32
NetBIOS over Tcpip. . . . . . . . : Disabled
Tunnel adapter Teredo Adapter:
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Media State . . . . . . . . . . . : Enabled
Connection-specific DNS Suffix
. :
Description . . . . . . . . . . . : Teredo Tunneling Pseudo-Interface
Physical Address. . . . . . . . . : 02-00-54-55-4E-01
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : 2001:0:4136:e37c:4e8:3426:7c94:fffe(Preferred)
Link-local IPv6 Address . . . . . : fe80::4e8:3426:53ef:f4f2%10(Preferred)
Default Gateway . . . . . . . . . : ::
NetBIOS over Tcpip. . . . . . . . : Disabled
The preceding command output displays three interfaces on this computer:

Local Area Connection (the installed network adapter)

ISATAP tunneling interface

Teredo tunneling interface
The Local Area Connection interface is an Ethernet network adapter and has both an IPv4
address (172.16.11.13) assigned by DHCP and a link-local IPv6 address
(fe80::3530:6107:45a2:a92c) that has been automatically assigned using IPv6 address
autoconfiguration. (You can recognize the link-local address by its address prefix, FE80::/64.)
The ―%8‖ appended to this address is the zone ID (or scope ID) that indicates which
connected portion of the network the computer resides on. This zone ID corresponds with the
interface index for the Local Area Connection interface. To view a list of interface indexes on a
computer, type netsh interface ipv6 show interface at a command prompt. For the example
computer, the output of this command is:
Idx
Met
MTU
State
Name
---
---
-----
-----------
-------------------
1
50
4294967295
connected
Loopback Pseudo-Interface 1
9
25
1280
connected
isatap.{9D607D7D-0703-4E67-82ED-9A8206377C5C}
10
10
1280
connected
Teredo Tunneling Pseudo-Interface
8
20
1500
connected
Local Area Connection
Here the Idx column indicates the interface index. The zone ID might be needed when
testing network connectivity with this computer from other computers using the ping and
tracert commands. See the section titled ―Troubleshooting IPv6 Connectivity‖ later in this
chapter for more information.
Returning to the output of the ipconfig /all command, the state of the link-local address
assigned to the LAN connection is Preferred, which indicates a valid IPv6 address you can use
to send and receive unicast IPv6 traffic.
The ISATAP tunneling interface has an autoconfigured link-local address of
fe80::5efe:172.16.11.13. The format for an ISATAP address is:
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
The first 64 bits are a unicast prefix that can be a link-local, global, or unique local
unicast IPv6 address prefix. This example uses the link-local address prefix because
no ISATAP router is present on the network. This means that the resulting ISATAP
address can be used only for communicating with other ISATAP hosts on the IPv4
network, and this ISATAP address is not registered in DNS servers.

The next 32 bits are either 0:5EFE (for a private IPv4 address) or 200:5EFE (for a
public IPv4 address) in an ISATAP address. (RFC 4214 also allows 100:5EFE and
300:5EFE in this portion of an ISATAP address.)

The final 32 bits consist of the 32-bit IPv4 address of the host in dotted-decimal
form (172.16.11.13 in this example).
Note
For more information on ISATAP addressing, see the white paper “IPv6
Transition Technologies” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=afe56282-290340f3-a5ba-a87bf92c096d &displaylang=en and the white paper “Intra-site
Automatic Tunnel Addressing Protocol Deployment Guide” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=0f3a8868-e33743d1-b271-b8c8702344cd &displaylang=en. See also the section titled
“Understanding ISATAP” later in this chapter.
The Teredo tunneling pseudo-interface displays the IPv6 address of the Teredo client as
2001:0:4136:e37c:4e8:3426:53ef:f4f2. The format for a Teredo client address is:

The first 32 bits are always the Teredo prefix, which is 2001::/32.

The next 32 bits contain the public IPv4 address of the Teredo server that helped in
the configuration of this Teredo address (here 4136:E37C hexadecimal, which
converts to 65.54.227.124 in dotted-decimal format). By default, the Teredo client in
Windows 7, Windows Vista and Windows Server 2008 automatically tries to
determine the IPv4 addresses of Teredo servers by resolving the name
teredo.ipv6.microsoft.com.

The next 16 bits are reserved for various Teredo flags.

The next 16 bits contain an obscured version of the external UDP port number that
corresponds to all Teredo traffic for this Teredo client. (The external UDP port
number is obscured XORing it with 0xFFFF, and in this example 0x3426 XOR 0xFFFF
= 0xCBD9 or decimal 52185, meaning UDP port 52185.)

The final 32 bits contain an obscured version of the external IPv4 address that
corresponds to all Teredo traffic for this Teredo client. (The external IPv4 address is
obscured, XORing it with 0xFFFF FFFF, and in this example is 0x7C94 FFFE XOR
0xFFFF FFFF = 0x836B 0001 or dotted-decimal 131.107.0.1.)
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IANA has allocated the IPv6 address prefix 2001::/32 for Teredo as of
January 2006. (See RFC 4830 at http://www.rfc-editor.org/rfc/rfc4380.txt for
details.) Windows XP–based clients originally used the 3FFE:831F::/32 Teredo
prefix. Windows XP–based clients with the Microsoft Security Bulletin MS06-064 at
http://www.microsoft.com/technet/security/Bulletin/MS06-064.mspx now use the
2001::/32 prefix.
Another way to display the IPv6 settings on a Windows 7 computer is to type the netsh
interface ipv6 show address command. The results for the computer in the preceding
example are:
Interface 1: Loopback Pseudo-Interface 1
Addr Type
DAD State
---------
----------- ---------- ---------- ------------------------
Valid Life Pref. Life Address
Other
Preferred
infinite
infinite ::1
Interface 9: isatap.{9D607D7D-0703-4E67-82ED-9A8206377C5C}
Addr Type
DAD State
---------
----------- ---------- ---------- ------------------------
Valid Life Pref. Life Address
Other
Preferred
infinite
infinite fe80::5efe:172.16.11.13%9
Interface 10: Teredo Tunneling Pseudo-Interface
Addr Type
DAD State
---------
----------- ---------- ---------- ------------------------
Valid Life Pref. Life Address
Public
Preferred
infinite
infinite 2001:0:4136:e37c:1071:3426:31d2:bfce
Other
Preferred
infinite
infinite fe80::1071:3426:31d2:bfce%10
Interface 8: Local Area Connection
Addr Type
DAD State
---------
----------- ---------- ---------- ------------------------
Other
Preferred
Note
Valid Life Pref. Life Address
infinite
infinite fe80::3530:6107:45a2:a92c%8
An advantage of displaying IPv6 address settings using the netsh interface
ipv6 show address command instead of ipconfig is that you can execute Netsh.exe
commands remotely against a targeted computer by using the –r
RemoteComputerName option.
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For more information on how to use ipconfig, Netsh.exe, and other tools to display IPv6
configuration information, see the article ―Using Windows Tools to Obtain IPv6 Configuration
Information‖ on Microsoft TechNet at http://technet.microsoft.com/enus/library/bb726952.aspx.
Direct from the Source: Explanation of Teredo States
With netsh int teredo show state, you can see the current state of Teredo, which can
be one of the following:
 Offline state In this state, something has failed and Teredo cannot be activated
(cannot be in the Qualified state) to be used by applications. Teredo enters this state in
three ways:

When the Administrator disables it via netsh int teredo set state disabled.

When Teredo detects that the computer is on a managed network
(detects the presence of a domain controller on the network—see the
section in this sidebar titled “Teredo in Enterprise Networks” for more
information), it will go offline if its type is not set to “enterpriseclient”.

When some internal mechanism has failed in Teredo, such as suddenly
being unable to reach the Teredo server or being unable to resolve
teredo.ipv6.microsoft.com. In only this case, Teredo will attempt to move
into the Dormant state using an exponential back-off time-out as follows:
wait 5 seconds, try again; wait 10 seconds, try again; wait 20 seconds, try
again; and continue until it tries every 15 minutes.
 Dormant state This is the state when Teredo is “enabled but not active.” IPv6 traffic
cannot flow over Teredo, but applications can trigger to activate Teredo. No edge
traversal will occur in this state. No traffic is sent to the Teredo servers.
 Probe state This is the transition state from Dormant to Qualified. In this state, Teredo
will try to establish communication with the Teredo server. If this succeeds, Teredo
moves to the Qualified state. If this fails, Teredo will go to the Offline state.
 Qualified state In this state, IPv6 traffic can flow into and out of the system over
Teredo and possibly traverse the edge firewall/NAT.
Teredo in Enterprise Networks
Whether a computer is domain-joined or in a workgroup doesn’t matter to Teredo.
Teredo looks only at the environment that the computer is in. If Teredo detects the
presence of a domain controller, it will assume that the network is managed. In this
case, Teredo will go offline and stay offline unless it was administratively set to
“enterpriseclient” using the command netsh interface teredo set state
enterpriseclient. Hence, Teredo will go to the Offline state on a workgroup computer
that is connected to a network with a domain controller. This is to avoid traversing the
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edge of a corporate network. Conversely, if you take a domain-joined laptop home,
Teredo will detect that it is no longer in a managed network and will go to the
Dormant state.
Note that if you disable Teredo via the DisabledComponents registry key, it will
override all the Teredo netsh settings.
Kalven Wu, Software Design Engineer in Test
Windows Core Networking
Configuring IPv6 in Windows 7 Using the User Interface
To configure the IPv6 settings for a network connection in Windows 7 using the user
interface, follow these steps:
1.
Open the Network And Sharing Center in Control Panel.
2.
Click Manage Network Connections and then double-click the connection you want to
configure.
3.
Click the Properties button and respond to the UAC prompt.
4.
Select Internet Protocol Version 6 (TCP/IPv6) and click Properties to open the Internet
Protocol Version 6 (TCP/IPv6) Properties sheet (see Figure 29-1).
5.
Configure the IPv6 settings for the network connection as desired.
6.
Optionally validate the new TCP/IP settings using the Windows Network Diagnostics
Troubleshooter.
Figure 29-1 IPv6 properties of a network connection.
By default, the IPv6 settings for a network connection are configured as follows:
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
Obtain An IPv6 Address Automatically This specifies that the physical or logical
interface associated with this connection uses stateful or stateless address
autoconfiguration to obtain its IPv6 address.

Obtain DNS Server Address Automatically This specifies that the physical or logical
interface associated with this connection uses stateful address autoconfiguration
(DHCPv6) to obtain the IPv6 addresses of preferred and alternate DNS servers.
By selecting Use The Following IPv6 Address, you can manually configure the IPv6 address
settings for a network connection by specifying the following:

IPv6 Address Type the unicast IPv6 address you want to assign to the physical or
logical interface associated with this connection in colon-hexadecimal form. If you
need to assign additional unicast IPv6 addresses to the interface, click the Advanced
button and then click the IP Settings tab.

Subnet Prefix Length Type the subnet prefix length for the IPv6 address you
assigned to the physical or logical interface associated with this connection. For
unicast IPv6 addresses, the subnet prefix length should almost always be specified as
64.

Default Gateway Type the unicast IPv6 address of the default gateway for the local
IPv6 subnet in colon-hexadecimal form. If you need to specify additional default
gateways, click the Advanced button and then click the IP Settings tab.
By selecting Use The Following DNS Server Addresses, you can manually specify IPv6
addresses for a preferred and an alternate DNS server to be used by your connection. If you
need to specify additional alternate DNS servers, click the Advanced button and then click the
DNS tab. The remaining settings on the DNS tab have similar functionality to those used for
configuring IPv4 address settings.
Note The Advanced TCP/IP Settings dialog box does not have a WINS tab because
IPv6 does not use NetBIOS for name resolution.
Configuring IPv6 in Windows 7 Using Netsh
To configure the IPv6 settings for a network connection in Windows 7 using the Netsh.exe
command, open a command prompt window with local administrator credentials and type
the appropriate Netsh.exe command from the netsh interface ipv6 context. Some examples of
IPv6 configuration tasks that can be performed from this context include:

To add the unicast IPv6 address 2001:DB8::8:800:20C4:0 to the interface named Local
Area Connection as a persistent IPv6 address with infinite valid and preferred
lifetimes, type the following command:
netsh interface ipv6 add address “Local Area Connection”
2001:DB8::8:800:20C4:0
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To configure a default gateway with unicast IPv6 address
2001:DB8:0:2F3B:2AA:FF:FE28:9C5A for the interface named Local Area Connection,
add a default route with this address specified as a next-hop address by typing the
following command:
netsh interface ipv6 add route ::/0 “Local Area Connection”
2001:DB8:0:2F3B:2AA:FF:FE28:9C5A

To configure a DNS server with unicast IPv6 address 2001:DB8:0:1::1 as the second
(alternate) DNS server on the list of DNS servers for the interface named Local Area
Connection, type the following command:
netsh interface ipv6 add dnsserver “Local Area Connection” 2001:DB8:0:1::1
index=2
For more information on using the netsh interface ipv6 context, type netsh interface ipv6
? at a command prompt.
Other IPv6 Configuration Tasks
The following section describes some additional IPv6 configuration tasks that network
administrators may need to know how to perform with Windows 7 computers.
Enabling or Disabling IPv6
You cannot uninstall IPv6 in Windows 7, but you can disable IPv6 on a per-adapter basis. To
do this, follow these steps:
1.
Open the Network And Sharing Center in Control Panel.
2.
Click Manage Network Connections and then double-click the connection you want to
configure.
3.
Clear the check box labeled Internet Protocol Version 6 (TCP/IPv6) and then click OK
(see Figure 29-2).
Note that if you disable IPv6 on all your network connections using the user interface
method as described in the preceding steps, IPv6 will still remain enabled on all tunnel
interfaces and on the loopback interface.
As an alternative to using the user interface to disable IPv6 on a per-adapter basis, you can
selectively disable certain features of IPv6 by creating and configuring the following DWORD
registry value:
HKLM\SYSTEM\CurrentControlSet\Services\tcpip6\Parameters\DisabledComponents
Table 29-7 describes the flag values that control each IPv6 feature. By combining these flag
values together into a bitmask, you can disable more than one feature at once. (By default,
DisabledComponents has the value 0.)
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Figure 29-2 Disabling IPv6 for a network connection.
Table 29-7 Bitmask Values for Disabling IPv6 Features in Windows 7
FLAG LOWORDER BIT
1
RESULT OF SETTING THIS BIT TO A VALUE OF 1
0
Disables all IPv6 tunnel interfaces, including ISATAP, 6to4, and Teredo
tunnels
1
Disables all 6to4-based interfaces
2
Disables all ISATAP-based interfaces
3
Disables all Teredo-based interfaces
4
Disables IPv6 over all non-tunnel interfaces, including LAN and Point-toPoint Protocol (PPP) interfaces
5
Modifies the default prefix policy table1 to prefer IPv4 over IPv6 when
attempting connections
For more information concerning the IPv6 prefix policy table, see the Cable Guy article ―Source and
Destination Address Selection‖ for IPv6 at http://technet.microsoft.com/en-us/library/bb877985.aspx.
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For example, by setting the value of DisabledComponents to 0xFF, you can simultaneously
disable IPv6 on all your network connections and tunnel interfaces. If you do this, IPv6 still
remains enabled on the loopback interface, however.
Note
For some examples of common flag combinations that can be used to enable
or disable different aspects of IPv6 functionality in Windows 7 and Windows Vista,
see the Cable Guy article “Configuring IPv6 with Windows Vista” at
http://technet.microsoft.com/en-us/library/bb878057.aspx.
Depending on your scenario, there are other ways of effectively disabling IPv6 on Windows
7 computers, including:

Disable the IP Helper service This service must be running for IPv6 transition
technologies such as ISATAP, Teredo, and 6to4 to function on the computer. This
service provides automatic IPv6 connectivity over an IPv4 network, and if the service
is stopped, the computer will have only IPv6 connectivity if it is connected to a native
IPv6 network. Therefore, if your network is not native IPv6, disabling this service on
Windows 7 computers effectively disables IPv6 on them. You can use Group Policy to
disable this service on targeted Windows 7 computers.

Use netsh to disable all IPv6 interfaces For example, the following commands will
disable all IPv6 transition technologies (Teredo, 6to4, and ISATAP):
netsh interface teredo set state disabled
netsh interface ipv6 6to4 set state state=disabled undoonstop=disabled
netsh interface ipv6 isatap set state state=disabled
You can include these commands in a script and send them inside an SCCM package
to disable transition technologies on targeted computers.

Configure Windows Firewall to block IPv6 traffic You could block incoming and
outgoing IPv6 protocol 41 (for ISATAP and 6to4) and UDP 3544 (for Teredo) traffic
using the Windows Firewall, and you can use Group Policy to push this out to
targeted computers. Businesses that implement perimeter firewalls may want to do
this as a best practice for safeguarding their networks.
Disabling Random Interface IDs
You can disable the default behavior of generating random interface IDs for nontemporary
autoconfigured public addresses (global addresses registered in DNS) and link-local
addresses by using the following command:
netsh interface ipv6 set global randomizeidentifiers=disabled
To re-enable the generating of random interface IDs, use the following command:
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netsh interface ipv6 set global randomizeidentifiers=enabled
Note
Disabling random interface IDs causes link-local addresses to revert to using
48-bit MAC-layer (or 64-bit EUI) addresses for generating the interface ID portion
of the address. In Windows, this happens immediately and does not require a
reboot.
Resetting IPv6 Configuration
To remove all user-configured IPv6 settings and restore the IPv6 configuration of a computer
to its default state, type the following command:
netsh interface ipv6 reset
You must reboot the computer for this command to take effect.
Displaying Teredo Client Status
To verify the current state of the Teredo client on your computer, open a command prompt
window using local administrator credentials, and then type the following command:
netsh interface teredo show state
For a Windows 7 computer on which Teredo is currently inactive, the typical output for this
command looks like this:
Teredo Parameters
--------------------------------------------Type
: default
Server Name
: teredo.ipv6.microsoft.com.
Client Refresh Interval : 30 seconds
Client Port
: unspecified
State
: dormant
Client Type
: teredo client
Network
: managed
NAT
: none (global connectivity)
Note
If your command output doesn’t contain all of the preceding information,
you probably started your command prompt session using standard credentials
instead of administrator credentials.
If you now start an IPv6-enabled application that uses Teredo, such as Windows Meeting
Space or Windows Remote Assistance, and then type the same Netsh command, the
command output typically now looks like this:
Teredo Parameters
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--------------------------------------------Type
: default
Server Name
: teredo.ipv6.microsoft.com.
Client Refresh Interval : 30 seconds
Client Port
: unspecified
State
: qualified
Client Type
: teredo client
Network
: managed
NAT
: restricted
Comparing these two command outputs shows that starting an application that uses
Teredo changes the Teredo client state from Dormant (inactive) to Qualified (active).
Note The output of the netsh interface teredo show state command also tells you
the type of NAT your computer is behind (if any). In the preceding example, the
computer is behind a restricted NAT. Teredo works well behind restricted and cone
NATs and can even work behind symmetric NATs, but communication between
certain types of NATs doesn’t work. If you plan to purchase a SOHO router for
broadband Internet connectivity, the best choice is a router that supports 6to4. For
more information on how Teredo works and on the different types of NATs, see
“Teredo Overview” at
http://www.microsoft.com/technet/network/ipv6/teredo.mspx.
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Troubleshooting IPv6 Connectivity
The standard approach for troubleshooting TCP/IP network connectivity issues on IPv4
networks is to follow these steps:
1.
Type ipconfig /all at a command prompt to verify the IPv4 configuration of the
computer that is experiencing the problem.
2.
If verifying the computer‘s IPv4 configuration doesn‘t resolve the issue, try using the
ping command to test for network connectivity, beginning with the local computer and
working outward until the cause of the problem is determined. Specifically, follow
these steps in order listed:
a.
Ping the IPv4 loopback address 127.0.0.1 to verify that TCP/IP is installed and
configured properly on the computer.
b. Ping the IPv4 address of the local computer.
c.
Ping the IPv4 address of the default gateway.
d. Ping the IPv4 address of an IPv4 host on a remote subnet.
Other TCP/IP troubleshooting steps you can use on IPv4 networks include:

Use the route print command to verify the configuration of the local computer‘s
routing table.

Use tracert to verify that intermediate routers are configured properly.

Use the pathping command to identify packet loss over multi-hop paths.

Clear the ARP cache by typing netsh interface ip delete arpcache at a command
prompt.

Verify the computer‘s DNS configuration, clear the DNS client resolver cache, and
verify DNS name resolution.
Note
For more information on how to systematically troubleshoot IPv4 connectivity
problems, read Chapter 32, “Troubleshooting Network Issues.”
Troubleshooting IPv6 network connectivity issues requires many of the same tools you use
when troubleshooting IPv4. However, you use some of these tools in a different way because
of the nature of IPv6 addressing and the way IPv6 is implemented in Windows 7 and Windows
Vista. The differences include:

You might need to specify a zone ID when attempting to verify IPv6 network
connectivity with a target host using the ping command. The syntax for using ping
with IPv6 is ping IPv6Address%ZoneID, where ZoneID is the zone ID (or scope ID)
of the sending interface. For example, if the target host has the link-local unicast
IPv6 address FE80::D3:00FF:FE28:9C5A, and the sending interface has a zone ID of 12,
to verify IPv6 connectivity with this host you would type ping
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FE80::D3:00FF:FE28:9C5A%12 at a command prompt. To determine the zone ID for
an interface, you can either use the ipconfig /all command or type netsh interface
ipv6 show interface at a command prompt. Note that since the zone ID is locally
defined, a sending host and a receiving host on the same link may have different
zone IDs. (Global and unique local unicast IPv6 addresses do not need a zone ID.)

You should view and clear the neighbor cache on your computer before attempting
to use ping to verify IPv6 network connectivity. The neighbor cache contains recently
resolved link-layer IPv6 addresses; you can view it by typing netsh interface ipv6
show neighbors and flush it by typing netsh interface ipv6 delete neighbors at an
elevated command prompt.

You should also view and clear the destination cache on your computer before
attempting to verify IPv6 network connectivity using ping. The destination cache
contains next-hop IPv6 addresses for destinations. You can view the cache by typing
netsh interface ipv6 show destinationcache; you can flush it by typing netsh
interface ipv6 delete destinationcache at an elevated command prompt.

You should use the –d option when attempting to trace the route to a remote IPv6
host using tracert, or the –n option when using pathping. These options prevent
these commands from performing DNS reverse queries on every near-side router
interface along the routing path. Using these options can help speed up the display
of the routing path.
Note
For more help on troubleshooting IPv6 network connectivity issues, see the
Cable Guy article “Troubleshooting IPv6” at http://technet.microsoft.com/en-
us/library/bb878005.aspx. See also Chapter 12, “Troubleshooting TCP/IP,” in the
online book TCP/IP Fundamentals for Microsoft Windows, which you can download
from http://www.microsoft.com/downloads/details.aspx?FamilyID=c76296fd-
61c9-4079-a0bb-582bca4a846f&displaylang=en.
Note
Disabling IPv4 can also be a useful troubleshooting technique for developers
who need to verify that their applications are IPv6-capable.
Planning for IPv6 Migration
Migrating your existing IPv4-based network infrastructure to IPv6 requires an understanding
of different IPv6 transition technologies that you can use achieve your goal. Windows 7,
Windows Vista and Windows Server 2008 support three transition technologies in particular:

ISATAP Stands for Intra-Site Automatic Tunnel Addressing Protocol, an address
assignment and automatic tunneling technology defined in RFC 4214 that you can
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use to provide unicast IPv6 connectivity between IPv6/IPv4 hosts (hosts that support
both IPv6 and IPv4) across an IPv4-based intranet (a private network whose
infrastructure hardware, such as routers, only supports IPv4 and not IPv6).

6to4 An address assignment and automatic tunneling technology defined in RFC
3056 that you can use to provide unicast IPv6 connectivity between IPv6/IPv4 hosts
and sites across the IPv4-based public Internet. 6to4 enables you to assign global
IPv6 addresses within your private network so that your hosts can reach locations on
the IPv6 Internet without needing a direct connection to the IPv6 Internet or an IPv6
global address prefix obtained from an IPv6-supporting ISP. (Communication
between a 6to4 site and a node on the IPv6 Internet requires the use of a 6to4 relay,
however.)

Teredo An address assignment and automatic tunneling technology defined in RFC
4380 that you can use to provide unicast IPv6 connectivity between IPv6/IPv4 hosts
across the IPv4 public Internet, even when the IPv6/IPv4 hosts are located behind
zero or more NATs. Teredo provides similar functionality to 6to4 but without
needing edge devices that support 6to4 tunneling.
Note
For more information on IPv4/v6 transition technologies, see the white paper
“IPv6 Transition Technologies” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=afe56282-290340f3-a5ba-a87bf92c096d&DisplayLang=en.
These three IPv6 transition technologies are supported by Windows 7, Windows Vista,
Windows Server 2008, Windows XP Service Pack 2, and Windows Server 2003 Service Pack 1.
Of the three, ISATAP is the primary transition technology that you should use for migrating an
existing IPv4-based intranet to IPv6; it is discussed further in the following sections. Teredo is
primarily useful in Small Office/Home Office (SOHO) networking environments, where NATenabled broadband routers provide Internet connectivity for users. (Think of Teredo as a
transition technology of last resort, because as IPv6 connectivity becomes ubiquitous, the
need for NAT traversal will decline until Teredo is no longer needed.)
How It Works: Blocking Teredo
Teredo is intended to be a consumer technology and has generally not been
recommended for enterprises. This is because Teredo requires the edge device to
allow all outbound UDP traffic. For example, because of security reasons, many
enterprise administrators do not want client computers on the corporate network to be
directly accessible from the Internet, and in that case turning off Teredo is a good
idea.
If administrators want to disable Teredo on their client computers or simply prevent it
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from working, they can do so in one of three ways:
 Block all outbound UDP traffic by default. (This is the only reliable “external” method.)
 Block name resolution of the Teredo DNS host name, which by default on Windows 7
computers is teredo.ipv6.microsoft.com. (This method, however, leaves an easy
workaround, because the user can hard-code IP addresses.)
 Use Group Policy or a script to create the following DWORD registry value, which turns
off Teredo on targeted Windows 7 computers. (This registry setting is not exposed by
default in Group Policy but can be pushed down using a custom ADMX file.)
HKLM\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\DisabledCompon
ents
You can specify the following settings for this value:

0x10 Setting this value will disable Teredo only on the computer.

0x01 Setting this value will disable all tunnel interfaces on the
computer.
If administrators want to support only native IPv6 in their networks, or if they don’t
want to support any IPv6 traffic until they deploy native IPv6, they can choose to turn
off all tunneling technologies using the second choice in the preceding list.
Understanding ISATAP
By default, the IPv6 protocol in Windows 7 automatically configures a link-local unicast IPv6
address of the form FE80::5EFE:w.x.y.z (for private IPv4 addresses) or FE80::200:5EFE:w.x.y.z (for
public IPv4 addresses). This address is a link-local ISATAP address, and it is assigned to the
ISATAP tunneling interface. Using their link-local ISATAP addresses, two ISATAP hosts (such as
Windows 7 computers) can communicate using IPv6 by tunneling across an IPv4-only network
infrastructure (such as a network whose routers forward only IPv4 packets and not IPv6
packets).
Note
In Windows 7 and in Windows Vista with Service Pack 1 or later, link-local
ISATAP addresses are automatically configured only if the name “ISATAP” (the
ISATAP router name) can be resolved. Otherwise, the ISATAP interface will be
media-disconnected. However, if you administratively enable ISATAP by using the
netsh interface isatap set state enabled command, the link-local address will be
configured regardless of whether the ISATAP router name can be resolved.
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With the addition of one or more ISATAP routers (IPv6-enabled routers that advertise
address prefixes, forward packets between ISATAP hosts and other ISATAP routers, and act as
default routers for ISATAP hosts) a variety of transition topologies become possible, including:

Connecting ISATAP hosts on an IPv4-only intranet to an IPv6-capable network

Connecting multiple ―islands‖ of ISATAP hosts through an IPv6-capable backbone
These configurations are possible because ISATAP routers advertise address prefixes that
enable ISATAP hosts (such as Windows 7 computers) to autoconfigure global or unique local
unicast IPv6 addresses.
Note Without the presence of an ISATAP router, ISATAP hosts running Windows
Vista RTM could only autoconfigure link-local unicast IPv6 addresses, which limited
IPv6 communications to between hosts on the IPv4-only intranet. This was changed
in Windows Vista SP1 so that without an ISATAP router, the interface will show
media-disconnected. In other words, Windows Vista SP1 won’t configure a linklocal ISATAP address when no ISATAP router is configured. The behavior in Windows
7 is the same as in Windows Vista SP1.
Note
For more information on how ISATAP works, see the white paper “IPv6
Transition Technologies” at
http://www.microsoft.com/downloads/details.aspx?FamilyID=afe56282-290340f3-a5ba-a87bf92c096d &displaylang=en.
Direct from the Source: ISATAP Interface Name
The ISATAP interface name is based on the DNS setting of the primary IPv4
interface of this ISATAP interface. For example, if the DNS suffix assigned to the
primary IPv4 interface of this ISATAP interface is contoso.com, the ISATAP interface
name will be isatap.contoso.com.
An alternate form of the ISATAP interface name is isatap.{GUID} where GUID is a
globally unique identifier. However, this GUID form is used to name the ISATAP
interface only if there is no DNS suffix setting on the primary IPv4 interface.
Xinyan Zan, Technical Lead
IPv6 Transition Technology
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Migrating an Intranet to IPv6
Best practices for migrating existing IPv4-based network infrastructures to IPv6 are still
evolving. Therefore, this section presents a general outline of how to migrate an intranet to
IPv6 and provides references to more detailed information on the subject for interested
readers.
The ultimate goal of IPv4 to IPv6 migration is to achieve an IPv6-only network
infrastructure that has IPv6-only hosts. From a practical standpoint, however, the lesser goal
of achieving a network infrastructure that supports both IPv6 and IPv4—and where hosts also
support both IPv6 and IPv4 but use mainly IPv6—is a more reasonable goal to aim for.
Achieving this goal is a lengthy process that involves seven main steps:
1.
Upgrading your applications and services
2.
Preparing your DNS infrastructure
3.
Upgrading your hosts
4.
Migrating from IPv4-only to ISATAP
5.
Upgrading your routing infrastructure
6.
Upgrading your DHCP infrastructure
7.
Migrating from ISATAP to native IPv6
Step 1: Upgrading Your Applications and Services
To prepare your applications and services for migration, you will need to upgrade existing
applications and services to support IPv6 in addition to IPv4. This may require upgrades from
ISVs and third-party vendors or custom coding on your part. Although the ultimate goal is for
all your applications and services to run native IPv6, a more appropriate target is to ensure
that they work with both IPv4 and IPv6.
For further guidance, see the MSDN topic ―IPv6 Guide for Windows Sockets Applications‖
at http://msdn2.microsoft.com/en-us/library/ms738649.aspx.
Step 2: Preparing Your DNS Infrastructure
You must prepare your DNS infrastructure to support the AAAA records used to resolve DNS
names to IPv6 addresses. This might require upgrading your existing DNS servers. The DNS
Server service of Windows Server 2008 and Windows Server 2003 supports dynamic
registration of AAAA records for unicast IPv6 addresses (excluding link-local addresses).
For more information on configuring Windows Server 2003 DNS servers to support IPv6
hosts, see Chapter 9, ―Windows Support for DNS,‖ in the online book TCP/IP Fundamentals for
Microsoft Windows, which can be found at http://technet.microsoft.com/enus/library/bb727009.aspx.
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Step 3: Upgrading Your Hosts
You may need to upgrade some of your hosts until all your hosts support both IPv6 and IPv4.
Windows platforms from Windows XP Service Pack 2 onward support both IPv4 and IPv6,
though full support for IPv6 functionality for built-in programs and services is only provided
in Windows Vista and later.
Step 4: Migrating from IPv4-only to ISATAP
After you‘ve prepared your applications, services, hosts, and DNS/DHCP infrastructure, you
can begin deploying ISATAP routers to create islands of IPv6 connectivity within your IPv4based intranet. You will need to add A records to the appropriate DNS zones so that your
ISATAP hosts can determine the IPv4 addresses of your ISATAP routers.
You may decide to deploy zero or more ISATAP routers for inter-ISATAP subnet routing
within your intranet, depending on the size of your intranet and the geographical distribution
of its sites. You may decide to deploy redundant ISATAP routers to provide consistent
availability of IPv6 address prefixes and other configuration settings for your ISATAP hosts.
You will also likely deploy one or more ISATAP routers to provide IPv6 connectivity between
your IPv4-based network infrastructure and the public IPv6 Internet as this evolves.
For more information on deploying ISATAP routers using different migration scenarios, see
the white paper ―Intra-site Automatic Tunnel Addressing Protocol Deployment Guide‖ at
http://www.microsoft.com/downloads/details.aspx?FamilyID=0f3a8868-e337-43d1-b271b8c8702344cd &displaylang=en.
Step 5: Upgrading Your Routing Infrastructure
After you have deployed ISATAP to enable IPv6 hosts to communicate over your IPv4 network
infrastructure, you should begin upgrading your network infrastructure (including routers,
gateways, and other access devices) to support IPv6. Rather than upgrading your
infrastructure to support only IPv6, a more reasonable upgrade goal is dual IPv4/IPv6 support.
In many cases, actual replacement of router hardware is not necessary. Because many modern
hardware routers support both IPv4 and IPv6 routing, the task of upgrading of your routing
infrastructure to support IPv6 becomes configuration, not replacement. As you enable IPv6
routing support for a subnet, also enable the DHCPv6 relay agent for the subnet.
Typically, you will begin upgrading your routing infrastructure early in your ISATAP
deployment by upgrading the core routers on your network backbone to support IPv6. This
will create islands of ISATAP hosts that connect to this backbone to communicate with other
IPv6 hosts anywhere in your intranet.
Step 6: Upgrading Your DHCP Infrastructure
You can optionally upgrade your routing and DHCP infrastructure to support DHCPv6 for
automatic assignment of global or unique local unicast IPv6 addresses or configuration
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settings for IPv4/IPv6 nodes on your network. By using DHCPv6, an IPv6 host can obtain
subnet prefixes and other IPv6 configuration settings. A common use of DHCPv6 is to
configure Windows 7–based client computers with the IPv6 addresses of DNS servers on the
network. (DNS servers are not configured through IPv6 router discovery.)
The DHCP Server service in Windows Server 2003 does not support stateful address
autoconfiguration or the DHCPv6 protocol. The DHCP Server role in Windows Server 2008,
however, supports both stateful and stateless IPv6 address autoconfiguration using DHCPv6.
The DHCP Client service in Windows 7, Windows Vista and Windows Server 2008 supports
address autoconfiguration using DHCPv6.
Just as with DHCP with IPv4, you also need to deploy and configure DHCPv6 relay agents
for each subnet containing Windows 7 clients. Many hardware routers already support a
DHCPv6 relay agent. You must configure relay agents with the IPv6 addresses of the DHCPv6
servers on your network. Relay agents can be configured but should not be enabled until you
deploy IPv6 routing on your subnets.
When you are ready to enable DHCPv6 on subnets, configure your IPv6 routers to set the
Managed Address Configuration and Other Stateful Configuration flags to the appropriate
values for stateful or stateless DHCPv6 operation. For more information, see the Cable Guy
article titled ―The DHCPv6 Protocol‖ at
http://www.microsoft.com/technet/technetmag/issues/2007/03/CableGuy/default.aspx.
Step 7: Migrating from ISATAP to Native IPv6
Finally, when all your network infrastructure devices support IPv6, you can begin to
decommission your ISATAP routers, because you no longer need them. Whether you will also
migrate your infrastructure and hosts to support only pure-IPv6 is a decision best left for the
distant future.
Direct from the Source: Tips and Tricks for Transitioning from
IPv4 to IPv6
When transitioning a network from IPv4-only to dual stack, there are several areas
that need to be paid special attention.
Addressing
This is actually one area that gets easier with IPv6, due to the huge address space
that it offers. In general, you will want to add to each individual network segment a
single IPv6 /64 prefix, even in cases where you have more than one IPv4 subnet
assigned to the same network (e.g., by using the secondary keyword on Cisco
routers). You should not need to use Unique Local Addresses, even for lab networks.
One exception might be that you do not want to use a routable /64 prefix for a
segment that is not connected to your organization’s globally routable space (i.e., it is
physically separate).
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Firewalls
Deploying IPv6 can present issues for an organization’s security team. Because
IPSec services are available in all IPv6 stacks, it is more common to see end-to-end
security implemented with IPv6-enabled desktops. When faced with end-to-end
encryption, a firewall administrator has one of two choices: either deny the traffic and
drop it at the perimeter, or allow it through unchecked, thus bypassing the ACLs and
other security enabled on the firewall. Note that this problem exists even with IPv6enabled firewalls.
Tunneling Technologies
Many transition technologies, such as ISATAP, 6to4, and manually configured IPv6in-IPv4 tunnels, encapsulate IPv6 packets inside IPv4 in order to transport them
across an IPv4-only part of your network. These packets are identified by the use of
IP protocol 41 in the encapsulating packet. If firewalls, ACLs, or other devices in your
network are not configured to forward these packets, then communications using
these technologies will break. Many home routers, for example, are configured by
default to only forward UDP and TCP protocols.
Here's a real life example: After configuring a router to provide IPv6 services at an
IANA meeting in Florida, IPv6 connectivity was not working. After some
troubleshooting with the service provider, I determined that their router was dropping
IP protocol 41, thus preventing IPv6 connectivity across the service provider’s IPv4only network.
Network Applications
When deciding to IPv6-enable an existing workflow or application, make sure to
consider all parts of the process. For example, while upgrading a web front end to
support IPv6, don’t forget to also enable the separate file store and backend
database servers as well, otherwise the workflow may appear to support IPv6 from
the front end, but will not be completed tested.
DNS
Many DNS products today support the AAAA records which are used to store nameto-address mappings for IPv6 end systems. However, that does not mean that they
support IPv6 lookups against the database—in some cases, this functionality must be
enabled through a configuration setting or an upgrade to the product itself. This is
another part of an end-to-end IPv6 workflow that needs to be considered.
Address Management
A simple way to enable IPv6 auto-configuration on your hosts is to configure your
edge routers to advertise an IPv6 prefix via Router Advertisements. This enables
IPv6-enabled operating systems, including Vista, Windows Server 2008, and
Windows 7, to configure itself with an IPv6 address. This method of configuration is
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considered stateless, as the router will not track which IPv6 addresses are configured
on which end system. When performing address auditing against these systems (to
investigate a security incident, for example), it is impossible to determine which host
was assigned a given IPv6 address at a particular time. At best, if you are lucky, the
router’s ARP tables will contain the necessary information, but more often than not,
you will be unable to track a specific IPv6 address to the host on which it was
configured.
Here's a real life example: At a previous job, I was contacted by the local office of the
United States Secret Service to investigate a threat made against a government
official. I was able to track the IPv4 address they provided me to a high school in the
school district where I worked, and to a specific classroom at a certain time, based on
DHCP logs and switch CAM tables. A student was subsequently identified as being in
the classroom alone at the time and admitted to sending the messages, which turned
out to be a hoax. Tracking down auto-configured IPv6 addresses at this level of detail
is nearly impossible.
Mike Owen, Network Engineer
Data and Storage Platform Division
Summary
This chapter described the features of IPv6 in Windows 7, provided an overview of how IPv6
works, and outlined best practices for migrating an existing IPv4-only network to IPv6. An IPv6
migration requires careful planning and a thorough understanding of how IPv6 works, and
Windows 7, together with Windows Server 2008 R2, provide the features and tools you need
to migrate your network successfully.
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Additional Resources
The following resources contain additional information and tools related to this chapter.
Related Information

Understanding IPv6, Second Edition by Joseph Davies (Microsoft Press, 2008). See
http://www.microsoft.com/MSPress/books/11607.aspx.

The IPv6 home page on Microsoft TechNet at http://technet.microsoft.com/enus/network/bb530961.aspx.

The IPv6 blog of Sean Siler, IPv6 Program Manager, http://blogs.technet.com/ipv6.

―IPv6 for Microsoft Windows: Frequently Asked Questions‖ at
http://www.microsoft.com/technet/network/ipv6/ipv6faq.mspx.

The white paper ―Introduction to IP Version 6‖ at
http://www.microsoft.com/downloads/details.aspx?FamilyID=CBC0B8A3-B6A4-4952BBE6-D976624C257C&displaylang=en.

The white paper ―IPv6 Transition Technologies‖ at
http://www.microsoft.com/downloads/details.aspx?FamilyID=afe56282-2903-40f3a5ba-a87bf92c096d &displaylang=en.

The white paper ―Intra-site Automatic Tunnel Addressing Protocol Deployment‖ at
http://www.microsoft.com/downloads/details.aspx?FamilyID=0f3a8868-e337-43d1b271-b8c8702344cd &displaylang=en.

The Cable Guy article ―Changes to IPv6 in Windows Vista and Windows Server
‗Longhorn‘‖ at http://technet.microsoft.com/en-us/library/bb878121.aspx.

The Cable Guy article ―Performance Enhancements in the Next Generation TCP/IP
Stack‖ at http://technet.microsoft.com/en-us/library/bb878127.aspx.

The Cable Guy article ―Understanding the IPv6 Routing Table‖ at
http://technet.microsoft.com/en-us/library/bb878115.aspx.

The Cable Guy article ―Manual Configuration for IPv6‖ at
http://technet.microsoft.com/en-us/library/bb878102.aspx.

―Using Windows Tools to Obtain IPv6 Configuration Information‖ on Microsoft
TechNet at
http://www.microsoft.com/technet/itsolutions/network/ipv6/ipv6config.mspx.

The Cable Guy article ―Troubleshooting IPv6‖ at http://technet.microsoft.com/enus/library/bb878005.aspx.

The Cable Guy article ―Source and Destination Address Selection for IPv6‖ found on
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Microsoft TechNet at http://technet.microsoft.com/en-us/library/bb877985.aspx.

―Domain Name System Client Behavior in Windows Vista‖ on Microsoft TechNet at
http://technet.microsoft.com/en-us/library/bb727035.aspx.

KB 929852, ―How to disable certain Internet Protocol version 6 (IPv6) components in
Windows Vista,‖ at http://support.microsoft.com/kb/929852.

KB 932134, ―An outdated network router may not function correctly when you use it
together with new networking features in Windows Vista,‖ at
http://support.microsoft.com/kb/932134.

KB 944007, ―Unable to access shares via IPv6 address due to the ‗:‘ character,‖ at
http://support.microsoft.com/kb/944007.

KB 934640, ―In Windows, Event Viewer incorrectly displays IPv6 addresses in event
descriptions,‖ at http://support.microsoft.com/kb/934640.

KB 946784, ―How to obtain the IPv6 Ready Logo for Windows Vista and for Windows
Server 2008 from IPv6 Forum,‖ at http://support.microsoft.com/kb/946784.

KB 929851, ―The default dynamic port range for TCP/IP has changed in Windows
Vista and in Windows Server 2008,‖ at http://support.microsoft.com/kb/929851.

Chapter 9, ―Windows Support for DNS,‖ and Chapter 12, ―Troubleshooting TCP/IP,‖
in the online book TCP/IP Fundamentals for Microsoft Windows, which you can
download from
http://www.microsoft.com/downloads/details.aspx?FamilyID=c76296fd-61c9-4079a0bb-582bca4a846f &displaylang=en.
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