Read Windows Server 2008 R2 Unleashed Online
Authors: Noel Morimoto
server database directory
/OfflineSign — Offline signing zone files, including key genera-
tion/deletion
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DnsCmd
The /config option of the DNSCMD was used to set the Global Names option of the DNS
server earlier in the chapter. There is no option in the DNS console to set this value.
The Internet is running out of IP addresses. To resolve this problem, a relatively new tech-
nology is being deployed to give us more addresses. This technology is IPv6 and is
completely integrated into Windows Server 2008 R2.
You might wonder why there is need for more address space when good old IPv4 provides
somewhere in the range of four billion addresses. Unfortunately, there are over 6 billion
people on the planet and, thus, not enough IP addresses for each and every person. In this
age of ever-advancing technologies and Internet-enabled devices, it isn’t uncommon for a
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single individual to utilize more than one IP address. For example, an individual might
have an Internet connection at home, a workstation in the office, an Internet-enabled
phone, and a laptop to use in a cafe. This problem will only become more exacerbated as
devices such as refrigerators and coffeemakers become part of the wired world.
IPv6, Internet Protocol Version 6, not only brings a number of new features, as reviewed
in Chapter 7, “Active Directory Infrastructure,” such as integrated IPSec, QoS, stateless
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Domain Name System and IPv6
configuration, and so on, but, more important, it will also provide over
340,000,000,000,000,000,000,000,000,000,000,000,000 unique addresses—that’s 3.4 x 1038!
As mentioned in an earlier chapter, IPv6 provides a number of new features over IPv4:
vastly improved address space, improved network headers, native support for auto address
configuration, and integrated support for IPSec and QoS.
Windows Server 2008 R2’s networking advances are mostly due to the new TCP/IP stack
introduced with IPv6 in Windows Server 2008. Highlighted in the following list are a few
of the features that are included with Windows Server 2008 R2, derived from the new
TCP/IP stack:
.
Dual IP layer architecture for IPv6—
Windows 2003 required a separate protocol
to be installed to enable IPv6 support; whereas in Windows Server 2008 R2, IPv6 is
enabled and supported by default. Windows Server 2008 R2 supports the new stack
that integrates IPv4 and IPv6, leveraging the fact that IPv4 and IPv6 share common
layers (transport and framing).
.
Windows Filtering Platform—
All layers of the TCP/IP stack can be filtered,
enabling Windows Filtering Platform to be more secure, stack integration.
.
Protocol stack off-load—
By off-loading TCP and/or other protocols to the
Network Driver Interface Specification (NDIS) miniport and/or network interface
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adapters, performance improvements can occur on traffic-intensive servers.
.
Restart-less configuration changes—
Leveraging the new TCP/IP stack’s ability to
retain configuration settings, server restarts to enable configuration changes are no
longer necessary.
In the United States, IPv6 is quietly making its way into the mainstream by starting at the
edge. Broadband providers in California such as Comcast have already implemented IPv6
for their customers. Countries like China with their recent implementations have opted to
move to IPv6 as a default.
NOTE
From an implementation perspective, Microsoft Internet Acceleration Server (ISA) 2006
does not support IPv6. As a matter of fact, installing the IPv6 protocol stack on an ISA
2006 server is a security risk as it exposes the server directly to the Internet. This has
made it difficult for many organizations to start deploying IPv6 in a meaningful way.
One of the few IPv6 ready applications is the DirectAccess technology introduced in
Windows Server 2008 R2. See Chapter 24, “Server-to-Client Remote Access and
DirectAccess,” for more details.
Going forward, Microsoft Forefront Threat Management Gateway 2010 (TMG) fully sup-
ports IPv6 and allows many organizations to step into the IPv6 world.
IPv6 Introduction
299
IPv6 Addressing
With the increased address space, there is a change in the addressing. IPv6 is 128 bits,
normally displayed in eight sets of four 16-bit hexadecimal digits. Hexadecimal digits
range from A through F and 0 through 9 (see Table 10.2).
TABLE 10.2
Number Conversion
Decimal
Hexadecimal
Binary
0
0
0000
1
1
0001
2
2
0010
3
3
0011
4
4
0100
5
5
0101
6
6
0110
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7
7
0111
8
8
1000
9
9
1001
10
A
1010
11
B
1011
12
C
1100
13
D
1101
14
E
1110
15
F
1111
The reason for displaying the digits in hexadecimal is to cut down on the length of the
address. For example, an IPv6 address in binary form would be as follows:
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0010000000000001 0000110110111000
1111101110010010 0000000000000000
0000000000000000 0000000000000000
1001000111000010 0000000000010010
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CHAPTER 10
Domain Name System and IPv6
This makes for a very long address to have to type in. However, displayed in hexadecimal,
the same address would be as follows:
FC00:0db8:fb92:0000:0000:0000:91c2:0012
This is much shorter. This can be abbreviated even more as the following:
FC00:db8:fb92::91c2:12
These methods of shortening the IPv6 address, such as the abbreviated form (more on this
later in the chapter), help make the IPv6 addressing more manageable.
Still, this is a huge change from the 32-bit IPv4 addressing, where an address would be
something like 172.16.1.11. Trying to remember 32 hexadecimal digits versus 4 decimal
numbers is a significant change, when DNS itself was created so that users would not have
to remember the 4 decimal numbers.
Comprehending IPv6 Addressing
Comprehending IPv6 addressing can become a steep uphill challenge, as well as hard on
the fingers due to all the typing. The addresses are so long that abbreviation mechanisms
and conventions are used to ease the burden. However, this makes learning the addressing
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that much more difficult.
Here are a few rules and tips to assist with the future IPv6 change, as well as some conven-
tions that reduce the typing needed to enter the addresses:
. IPv6 DNS records show as AAAA records (or quad A).
. With IPv6 prefixes, a / slash in IPv6 defines the network with addresses (for example,
fc00:db8:1234::/48 is fc00:1234:5678:0000:0000:0000:0000:0000 through
FC00:0db8:1234:FFFF: FFFF: FFFF: FFFF: FFFF). Thus, FC00:db8:1234::/48 implies that
the first 48 bits are assigned to the network portion of the address—4 bits for each
hexadecimal digit, visible or not, totaling 16 bits for each segment and 48 bits for
three segments. This leaves 80 bits remaining out of a total of 128 bits in the
address. 80 bits translates into five groups of four hexadecimal digits. Because each
hexadecimal digit represents 4 bits, four multiplied by four, and then by five (for the
five groupings), makes 80. After you get the hang of it, it is similar to dealing with
“/24” being three groups of eight represented as 255.255.255.0 in IPv4.
. With IPv6 zero compression, consecutive groups of zeros can be subbed with a dou-
ble “:” (colon). This means that FC00:db8:bc92:0000:0000:1293:91c2:0012 would be
the same as FC00:db8:fb92::1293:91c2:0012.
NOTE
The caveat is that there can be only one double colon used in an IPv6 address to com-
press consecutive groups of zeros. Otherwise, it would not be possible to determine
how many zeros were compressed.
IPv6 Introduction
301
. RFC 2732 dictates that IPv6 address can be used in a URL syntax. As an example,
FBAC:FA9A:B6A54:3910:A81C:C1A8:B6A4:A2BB can be literally used in a URL as
long as it is enclosed in brackets [ and ], as seen in this example:
http://[FBAC:FA9A:B6A54:3910:A81C:C1A8:B6A4:A2BB].
. Loopback for IPv6 is ::1. This might be the only case where an IPv6 address is shorter
than the equivalent IPv4 address.
These conventions make it much easier to enter the addresses, if not quite as easy as
IPv4 addresses.
NOTE
The fc00::/7 prefix is the private reserved IPv6 address range. The private ranges in
IPv6 are called the unique local addresses (ULA) and are not globally routable. This is
equivalent to the 10.x.x.x, 172.16-31.x.x, and 192.168.x.x IPv4 private addresses.
The unique local address range (fc00::/7) is further divided into 2 /8 address ranges.
The first is the fc00::/8 range, which is available for private use. The second is the
fd00::/8 range, which is to include a random 40-bit string. The local link address is
assigned the fe80::/10 range, which is from the second range.
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IPv6 Transition Technologies
IPv6 is most likely to be deployed in an IPv4 world today, given the prevalence of IPv4 in
the Internet today. This creates an IPv4 gap across which IPv6 devices need to communi-
cate. Figure 10.18 shows the gap between IPv6 devices.
?
IPv4 Network
?
Gap
IPv6 Device
IPv6 Device
FIGURE 10.18
The IPv4 gap between IPv6 devices.
Most organizations will need to use IPv6 transition technologies to bridge the IPv4 gap
from their IPv6-enlightened devices to communicate. Figure 10.19 shows the IPv4/IPv6
protocol stacks in place of the devices shown in the previous figure.
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Application Layer
Application Layer
IPv4 Network
Transport Layer
Transport Layer
IPv4
IPv4
IPv6 Device
IPv6
IPv6
IPv6 Device
Network Layer
Network Layer
FIGURE 10.19
Bridging the IPv4 gap with transition technologies.
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CHAPTER 10
Domain Name System and IPv6
Communications between IPv6 devices (either hosts or routers) over IPv4 networks is
accomplished with IPv6 over IPv4 tunneling. In tunneling, the IPv6 packets are encapsu-
lated in an IPv4 packet by the source device and routed through the IPv4 network. When
the encapsulated packet arrives at the boundary between the IPv4 and IPv6 networks, the
IPv4 encapsulation is stripped off and the IPv6 packet continues on its way.
Older operating systems such as Windows 2003 and Windows XP implemented a dual
protocol stack to support IPv6. This essentially duplicates the Transport layer, including
the TCP and UDP protocols. These are the workhorse protocols of the Internet, and the
dual-stack architecture is very inefficient and introduces a lot of overhead. Windows 2008
R2, Windows 2008, Windows 7, and Windows Vista have a modern protocol dual IP layer
architecture that is designed from the ground up to support IPv6. This architecture is
much more efficient and performs much better. Figure 10.20 shows the two architectures.
Application Layer
Application Layer
Transport
Transport
Transport Layer
Layer
Layer
IPv6
IPv4
IPv6
IPv4
Network Layer
Network Layer
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Dual IP Layer
Dual Stack
Architecture
Architecture
FIGURE 10.20
Dual IP layer and dual-stack architectures.
These transition protocols provide tunneling of IPv6 traffic through IPv4 network by
encapsulating the IPv6 packet in an IPv4 packet, as shown in Figure 10.21.
IPv6 Packet
IPv6
EXTENSION
PACKET
HEADER
HEADER
PAYLOAD
IPv6
IPv6
EXTENSION
PACKET
HEADER
HEADER
HEADER
PAYLOAD
Pv4 Packet
FIGURE 10.21
IPv6 packet encapsulation in an IPv4 packet.
IPv6 Introduction
303
The IETF RFC2893, “Transition Mechanisms for IPv6 Hosts and Routers,” defines the IPv4
compatibility mechanisms for tunneling IPv6 over IPv4. The RFC defines two types of
tunnels, specifically:
.
Configured tunnels—
These are tunnels that are manually configured with the
static routes through the IPv4 network.
.
Automatic tunnels—
These tunnels don’t require manual configuration, as they are
derived from the IPv4 addresses of the devices. Windows supports the ISATAP, 6to4,
and Teredo automatic tunneling protocols.
NOTE
In Windows, static tunneling routes can be added with the netsh interface ipv6
add v6v4tunnel command.
Most IPv6 tunnels are automatic tunnels, due to the ease of configuration. ISATAP and