Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP). IPv6 is intended to correct many of the shortcomings of IPv4, which was the previous version of the IP.

In Microsoft Exchange Server 2013, IPv6 is fully supported, but only when IPv4 is also installed. You can disable IPv4 so only IPv6 is enabled, but uninstalling IPv4 isn't supported. If Exchange 2013 is deployed in this configuration, all Exchange servers can send data to and receive data from devices, servers, and clients that use IPv6 addresses.

This topic discusses IPv6 addressing in Exchange 2013. For additional background information about IPv6, see IPv6.

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IPv6 support in Exchange 2013 components

Enable or disable protocols in the operating system

IPv6 address basics

The following table describes the components in Exchange 2013 affected by IPv6.

Exchange 2013 features and IPv6

Feature	IPv6 supported	Comments
IP Allow list and IP Block list in the Connection Filtering agent	Yes
IP Allow List providers and IP Block List providers in the Connection Filtering agent.	No	Currently, there is no widely accepted industry standard protocol for looking up IPv6 addresses. Most IP Block List providers don't support IPv6 addresses. 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.
Sender reputation in the Protocol Analysis agent	No	The Protocol Analysis agent doesn't compute the sender reputation level (SRL) for messages that originate from IPv6 senders. For more information about sender reputation, see Sender Reputation and the Protocol Analysis Agent.
Sender ID	Yes	For more information, see Sender ID.
Receive connectors	Yes	IPv6 addresses are accepted for the following components: Local IP address bindings Remote IP addresses 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.
Send connectors	Yes	IPv6 addresses are accepted for the following components: Smart host IP addresses The SourceIPAddress parameter for Send connectors 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 mail exchange (MX) records are configured correctly. This helps ensure message delivery if a remote messaging server tries any kind of reverse lookup test on the specified IPv6 address. For more information, see Send Connectors.
Incoming message rate limits	Partial	Incoming message rate limits that you can set on a Receive connector, such as the MaxInboundConnectionPercentagePerSource parameter, the MaxInboundConnectionPerSource parameter, and the TarpitInterval parameter, only apply to a global IPv6 address. Link local IPv6 addresses and site local IPv6 addresses aren't affected by any specified incoming message rate limits.
Unified Messaging	Yes	For more information, see IPv6 Support in Unified Messaging.
Database availability group member	Yes	Static IPv6 addresses are supported by Windows Server 2008 and the Cluster service. However, using static IPv6 addresses goes against best practices. Exchange 2013 on Windows Server 2008 doesn't support the configuration of static IPv6 addresses during setup. Failover clusters support Intra-site Automatic Tunnel Addressing Protocol (ISATAP). They support only IPv6 addresses that allow for dynamic registration in DNS. Link local addresses can't be used in a cluster.

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Exchange servers fully support IPv6 networks. Therefore, even if you aren't using IPv6, you don't need to disable IPv6 on your Exchange servers.

IPv6 support in Exchange 2013 requires IPv4 to be installed on all Exchange 2013 servers. If you don't need IPv4 in your organization, you can disable IPv4 on your Exchange 2013 servers. Uninstalling IPv4 from your Exchange 2013 servers isn't supported.

To learn more about IPv6 support in Microsoft Windows, see IPv6 for Microsoft Windows: Frequently Asked Questions.

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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 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 examples of the IPv6 address notation and the equivalent IPv6 address syntax.

IPv6 address notation and syntax

IPv6 address notation	IPv6 address syntax
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 are 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 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 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.

IPv4 vs. IPv6 elements

Item	IPv4	IPv6
Private IP address	10.0.0.0/8 172.16.0.0/12 192.168.0.0/16	FD00::/8
Link local address	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)
Domain Name System (DNS) host name resolution	Address record (A record)	AAAA record or A6 record

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

Supported IPv6 Address Input Formats