IPv6 is a new version of the Internet Protocol. The current version of the Internet Protocol is known as Internet Protocol Version 4 (IPv4). IPv6 is intended to correct many of the shortcomings of IPv4, such as a decreasing pool of available addresses, lack of extensibility, and lack of autoconfiguration. For example, IPv6 addresses are 128-bits long. In contrast, IPv4 addresses are 32-bits long. There are enough IPv6 addresses for every person on earth to have trillions and trillions of IPv6 addresses assigned to them.

Because IPv4 and IPv6 are completely different protocols, an IPv4 network can't communicate directly with an IPv6 network, and vice versa. Network administrators deploy devices, such as routers, that can route information between IPv4 networks and IPv6.

Although IPv6 was officially defined in RFC 2460 in 1996, native IPv6 environments are rare. Most administrators deploy a dual environment where both IPv4 and IPv6 are configured and supported on the network.

For more information about IPv6, see IPv6.

IPv6 is supported in the following Microsoft server operating systems:

• Windows Server 2008   By default, the IPv6 protocol and the IPv4 protocol are both installed and enabled. When both IPv4 and IPv6 are enabled, IPv6 is given preference over IPv4. Additionally, you can remove the IPv4 protocol so that the server runs IPv6 exclusively.
  
• Windows Server 2003   By default, the IPv6 protocol isn't installed. However, it can be added. You can't uninstall the IPv4 protocol if the IPv6 protocol is installed.
  

IPv6 is supported in the following Microsoft desktop operating systems:

• Windows Vista   By default, the IPv6 protocol and the IPv4 protocol are both installed and enabled. When both IPv4 and IPv6 are enabled, IPv6 is given preference over IPv4. Additionally, you can remove the IPv4 protocol so that the computer runs IPv6 exclusively.
  
• Windows XP Service Pack 1 (SP1) or later   By default, the IPv6 protocol isn't installed. However, it can be added. You can't uninstall the IPv4 protocol if the IPv6 protocol is installed.
  

IPv6 is only supported in Exchange 2007 SP1 when it is installed on a Windows Server 2008 computer that has both IPv4 and IPv6 enabled. If you disable the IPv4 protocol, Exchange 2007 SP1 can't support IPv6.

Also, remember also that Exchange management tasks can be run remotely so that you can configure any Exchange server in your organization from the management interfaces of any other Exchange server or from a workstation that has the administrative tools installed. The IP addressing capabilities are limited by the target of the operation, not by the computer on which the task is run.

An IPv6 address is 128-bits long. The address is described by using colon-hexadecimal notation. Colon-hexadecimal notation describes the 128-bit address by using eight 16-bit, 4-digit hexadecimal numbers that are separated by the colon character ( : ). An example of an IPv6 address in colon-hexadecimal notation is 2001:0DB8:0000:0000:02AA:00FF:C0A8:640A.

You can express an IPv6 address by using the following methods:

• Suppress leading zeros   You can omit the leading zeros in any of the eight 4-digit hexadecimal numbers in an IPv6 address.
  
• Double-colon compression   You can use two colons ( :: ) to represent contiguous 16-bit hexadecimal digits that contain all zeros. These all-zero digits may exist at the beginning, middle, or end of the IPv6 address. You can only use double-colon compression one time in an IPv6 address.
  
• Trailing dotted decimal notation   You may express the last 32 bits at the end of an IPv6 address in dotted-decimal notation by separating the 8-bit digits with a period ( . ). Trailing dotted-decimal notation is frequently used with IPv4-compatible addresses.
  

The following table provides a comparison of the equivalent IPv6 address syntax is described.

A comparison of the equivalent IPv6 address syntax

IPv6 address notation	IPv6 address
Full IPv6 address	2001:0DB8:0000:0000:02AA:00FF:C0A8:640A
IPv6 address that uses suppressed leading zeros	2001:DB8:0:0:2AA:FF:C0A8:640A
IPv6 address that uses double-colon compression	2001:DB8::2AA:FF:C0A8:640A
IPv6 address that uses trailing dotted-decimal notation	2001:DB8::2AA:FF:192.168.100.10

IPv6 addresses may be categorized into the following types:

• Unicast address   A packet is delivered to one interface.
  
• Multicast address   A packet is delivered to multiple interfaces.
  
• Anycast address   A packet is delivered to the nearest of multiple interfaces. The distance between interfaces is defined by the routing cost.
  

IPv6 unicast addresses have the following possible scopes:

• Link-local   The scope of the IPv6 address is the local subnet. IPv6 link local addresses are comparable to IPv4 link local addresses that are used in Automatic Private IP Addressing (APIPA).
  
• Site-local   The scope of the IPv6 address is the local organization. Site local addresses were deprecated by RFC 3879 and replaced by unique local addresses as defined in RFC 4193. IPv6 site local addresses and IPv6 unique local addresses are comparable to IPv4 private IP addresses.
  
• Global   The scope is of the IPv6 address is the whole world. IPv6 global addresses are comparable to IPv4 public IP addresses.
  

The following table provides a comparison of IPv4 elements and IPv6 elements.

A comparison of IPv4 elements and IPv6 elements

Item	IPv4	IPv6
Private IP addresses	10.0.0.0/8 172.16.0.0/12 192.168.0.0/16	FD00::/8
Link local addresses	169.254.0.0/16	FE80::/64
Loopback address	127.0.0.1	::1
Unspecified address	0.0.0.0	::
Address resolution	Address Resolution Protocol (ARP)	Neighbor Discovery (ND)
DNS host name resolution	"A" record	"AAAA" record or "A6" record

For more information about IPv6 addressing, see IPv6 Address Types.

Supported IPv6 Input Formats in Exchange 2007 SP1 on Windows Server 2008

The following table describes the components in Exchange 2007 SP1 that are directly affected by IPv6. If a component is not mentioned, you can assume that it is unaffected by IPv6 addressing and functions correctly.

Exchange 2007 SP1 components that are directly affected by IPv6

Source	Feature	IPv6 supported?	Comments
Transport	IP Allow List and IP Block List	Yes	For more information about the IP Allow list, see How to Add IP Addresses to the IP Allow List and IP Block List.
Transport	IP Allow List providers and IP Block List providers	No	Currently, there is no widely accepted industry standard protocol for looking up IPv6 addresses. Most IP Block List providers do not support IPv6 addresses. Therefore, if you allow anonymous connections from unknown IPv6 addresses on a Receive connector, you increase the risk that spammers will bypass IP Block List providers and successfully deliver spam into your organization. For more information about the IP Block list providers, see How to Configure IP Allow List and IP Block List Providers.
Transport	Sender reputation	No	The Protocol Analysis agent does not compute the sender reputation level (SRL) for messages that originate from IPv6 senders. For more information about sender reputation, see Sender Reputation.
Transport	Sender ID	Yes	For more information, see Sender ID.
Transport	Receive connectors	Yes	IPv6 addresses are accepted for the following components: Local IP address bindings Remote IP addresses and IP address ranges We strongly recommend against configuring Receive connectors to accept anonymous connections from unknown IPv6 addresses. If your organization must receive mail from senders who use IPv6 addresses, create a dedicated Receive connector that restricts the remote IP addresses to the specific IPv6 addresses that those senders use. For more information, see Receive Connectors.
Transport	Send connectors	Yes	IPv6 addresses are accepted for the following components: Smart host IP addresses The SourceIPAddress parameter for Send connectors that are configured on Edge Transport servers Note: If you want to specify an IPv6 address for the SourceIPAddress parameter, make sure that the appropriate DNS AAAA and MX records are configured correctly. This helps ensure message delivery if a remote messaging server tries any kind of reverse look-up test on the specified IPv6 address. For more information, see Send Connectors.
Transport	Incoming message rate limits	Partial	Incoming message rate limits that you can set on a Receive connector, such as MaxInboundConnectionPercentagePerSource parameter, the MaxInboundConnectionPerSource parameter, and the TarpitInterval parameter only apply to global IPv6 address. Link local IPv6 addresses and site local IPv6 addresses are not affected by any specified incoming message rate limits. For more information about incoming message rate limits, see Managing Message Throttling.
Unified Messaging	All features	No	Unified Messaging doesn't support IPv6 in any version of Exchange 2007. For more information, see Unified Messaging.
High Availability	IPv6 addresses	Yes	Static IPv6 addresses are supported by Windows Server 2008 and the Microsoft Windows Cluster service. However, using static IPv6 addresses goes against best practices. Therefore, Exchange 2007 SP1 on Windows Server 2008 doesn't support configuring static IPv6 addresses during setup. Failover clusters support Intrasite Automatic Tunneling Addressing Protocol (ISATAP). They support only IPv6 addresses that allow for dynamic registration in DNS. Therefore, link local addresses can't be used in a cluster. For more information, see New High Availability Features in Exchange 2007 SP1.
Outlook Anywhere	DSProxy component	No	When a client that is using Outlook Anywhere tries to connect to Exchange 2007 SP1 running on Windows Server 2008, the client cannot connect. This happens because the RPCProxy component on the Client Access server that is running under Windows Server 2008 cannot connect through port 6004 to the DSProxy component on the Exchange Mailbox server. For more information, see Outlook Anywhere Client Connectivity Issue Because of TCP/IPv6

If you experience any of the issues described above, you can resolve the issues by disabling IPv6 on your Exchange servers. To help you do this, use the instructions listed in IPv6 for Microsoft Windows: Frequently Asked Questions. You can also use these instructions to re-enable IPv6 on your Exchange servers if needed.