To disable the IPv6 VPN protocol on Mac via Network settings: 1) Click on System Preferences. 2) Open Network. 3) Select the network that you are currently using and click on Advanced. 4) Set Configure IPv6 to Off. To disable the IPv6 VPN protocol on Mac via Terminal commands: 1) Open Terminal.
- IPv6 Tutorial
By default, Tunnelblick disables IPv6 while a VPN is connected. This is done to prevent information leaks in common VPN setups (see A Glance through the VPN Looking Glass: IPv6 Leakage and DNS Hijacking in Commercial VPN clients). To fix this problem: Verify with your VPN service provider that no information is leaked if IPv6 traffic is allowed. CIDR notation is a standard syntax for writing IPv6 addresses with a routing prefix. It consists of an IPv6 address, a slash, then a number of bits to measure the routing prefix. 2002::1234:abcd:ffff:c0a8:101/64 is an example of IPv6 CIDR notation.
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Ipv6 Mac Address
The wonder of IPv6 lies in its header. An IPv6 address is 4 times larger than IPv4, but surprisingly, the header of an IPv6 address is only 2 times larger than that of IPv4. IPv6 headers have one Fixed Header and zero or more Optional (Extension) Headers. All the necessary information that is essential for a router is kept in the Fixed Header. The Extension Header contains optional information that helps routers to understand how to handle a packet/flow.
Fixed Header
IPv6 fixed header is 40 bytes long and contains the following information.
| S.N. | Field & Description |
|---|---|
| 1 | Version (4-bits): It represents the version of Internet Protocol, i.e. 0110. |
| 2 | Traffic Class (8-bits): These 8 bits are divided into two parts. The most significant 6 bits are used for Type of Service to let the Router Known what services should be provided to this packet. The least significant 2 bits are used for Explicit Congestion Notification (ECN). |
| 3 | Flow Label (20-bits): This label is used to maintain the sequential flow of the packets belonging to a communication. The source labels the sequence to help the router identify that a particular packet belongs to a specific flow of information. This field helps avoid re-ordering of data packets. It is designed for streaming/real-time media. |
| 4 | Payload Length (16-bits): This field is used to tell the routers how much information a particular packet contains in its payload. Payload is composed of Extension Headers and Upper Layer data. With 16 bits, up to 65535 bytes can be indicated; but if the Extension Headers contain Hop-by-Hop Extension Header, then the payload may exceed 65535 bytes and this field is set to 0. |
| 5 | Next Header (8-bits): This field is used to indicate either the type of Extension Header, or if the Extension Header is not present then it indicates the Upper Layer PDU. The values for the type of Upper Layer PDU are same as IPv4’s. |
| 6 | Hop Limit (8-bits): This field is used to stop packet to loop in the network infinitely. This is same as TTL in IPv4. The value of Hop Limit field is decremented by 1 as it passes a link (router/hop). When the field reaches 0 the packet is discarded. |
| 7 | Source Address (128-bits): This field indicates the address of originator of the packet. |
| 8 | Destination Address (128-bits): This field provides the address of intended recipient of the packet. |
Extension Headers
In IPv6, the Fixed Header contains only that much information which is necessary, avoiding those information which is either not required or is rarely used. All such information is put between the Fixed Header and the Upper layer header in the form of Extension Headers. Each Extension Header is identified by a distinct value.
When Extension Headers are used, IPv6 Fixed Header’s Next Header field points to the first Extension Header. If there is one more Extension Header, then the first Extension Header’s ‘Next-Header’ field points to the second one, and so on. The last Extension Header’s ‘Next-Header’ field points to the Upper Layer Header. Thus, all the headers points to the next one in a linked list manner.
If the Next Header field contains the value 59, it indicates that there are no headers after this header, not even Upper Layer Header.
The following Extension Headers must be supported as per RFC 2460:
The sequence of Extension Headers should be:
These headers:
1. should be processed by First and subsequent destinations.
2. should be processed by Final Destination.
Extension Headers are arranged one after another in a linked list manner, as depicted in the following diagram:
Windows Vista, Windows Server 2008, and later versions of Windows implement RFC 3484 and use a prefix table to determine which address to use when multiple addresses are available for a Domain Name System (DNS) name.
By default, Windows favors IPv6 global unicast addresses over IPv4 addresses.
Applies to: Windows 10 - all editions, Windows Server 2019, Windows Server 2016, Windows Server 2012 R2
Original KB number: 929852
Summary
It is common for IT administrators to disable IPv6 to troubleshoot networking-related issues such as name resolution issues.
Important
Internet Protocol version 6 (IPv6) is a mandatory part of Windows Vista and Windows Server 2008 and newer versions. We do not recommend that you disable IPv6 or its components. If you do, some Windows components may not function.
We recommend using Prefer IPv4 over IPv6 in prefix policies instead of disabling IPV6.
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Use registry key to configure IPv6
Important
Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restoration in case problems occur.
The IPv6 functionality can be configured by modifying the following registry key:
Location: HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpip6Parameters
Name: DisabledComponents
Type: REG_DWORD
Min Value: 0x00 (default value)
Max Value: 0xFF (IPv6 disabled)
| IPv6 Functionality | Registry value and comments |
|---|---|
| Prefer IPv4 over IPv6 | Decimal 32 Hexadecimal 0x20 Binary xx1x xxxx Recommended instead of disabling IPv6. |
| Disable IPv6 | Decimal 255 Hexadecimal 0xFF Binary 1111 1111 See startup delay occurs after you disable IPv6 in Windows if you encounter startup delay after disabling IPv6 in Windows 7 SP1 or Windows Server 2008 R2 SP1. Additionally, system startup will be delayed for five seconds if IPv6 is disabled by incorrectly, setting the DisabledComponents registry setting to a value of 0xffffffff. The correct value should be 0xff. For more information, see Internet Protocol Version 6 (IPv6) Overview. The DisabledComponents registry value doesn't affect the state of the check box. Even if the DisabledComponents registry key is set to disable IPv6, the check box in the Networking tab for each interface can be checked. This is an expected behavior. You cannot completely disable IPv6 as IPv6 is used internally on the system for many TCPIP tasks. For example, you will still be able to run ping ::1 after configuring this setting. |
| Disable IPv6 on all nontunnel interfaces | Decimal 16 Hexadecimal 0x10 Binary xxx1 xxxx |
| Disable IPv6 on all tunnel interfaces | Decimal 1 Hexadecimal 0x01 Binary xxxx xxx1 |
| Disable IPv6 on all nontunnel interfaces (except the loopback) and on IPv6 tunnel interface | Decimal 17 Hexadecimal 0x11 Binary xxx1 xxx1 |
| Prefer IPv6 over IPv4 | Binary xx0x xxxx |
| Re-enable IPv6 on all nontunnel interfaces | Binary xxx0 xxxx |
| Re-enable IPv6 on all tunnel interfaces | Binary xxx xxx0 |
| Re-enable IPv6 on nontunnel interfaces and on IPv6 tunnel interfaces | Binary xxx0 xxx0 |
Note
- Administrators must create an .admx file to expose the registry settings of below table in a Group Policy setting.
- You must restart your computer for these changes to take effect.
- Values other than 0 or 32 causes the Routing and Remote Access service to fail after this change takes effect.
By default, the 6to4 tunneling protocol is enabled in Windows when an interface is assigned a public IPv4 address (Public IPv4 address means any IPv4 address that isn’t in the ranges 10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16). 6to4 automatically assigns an IPv6 address to the 6to4 tunneling interface for each address, and 6to4 dynamically registers these IPv6 addresses on the assigned DNS server. If this behavior isn’t desired, we recommend disabling the IPv6 tunnel interfaces on the affected hosts.
You can also follow these steps to modify the registry key:
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Open an administrative Command Prompt window.
Run the following command:
Note
Replace the <value> with the corresponding value.
How to calculate the registry value
Windows use bitmasks to check the DisabledComponents values and determine whether a component should be disabled.
To learn which component each bit (from low to high) controls, refer to the following table.
| Name | Setting |
|---|---|
| Tunnel | Disable tunnel interfaces |
| Tunnel6to4 | Disable 6to4 interfaces |
| TunnelIsatap | Disable Isatap interfaces |
| Tunnel Teredo | Disable Teredo interfaces |
| Native | Disable native interfaces (also PPP) |
| PreferIpv4 | Prefer IPv4 in default prefix policy |
| TunnelCp | Disable CP interfaces |
| TunnelIpTls | Disable IP-TLS interfaces |
For each bit, 0 means false and 1 means true. Refer to the following table for an example.
| Setting | Prefer IPv4 over IPv6 in prefix policies | Disable IPv6 on all nontunnel interfaces | Disable IPv6 on all tunnel interfaces | Disable IPv6 on nontunnel interfaces (except the loopback) and on IPv6 tunnel interface |
|---|---|---|---|---|
| Disable tunnel interfaces | 0 | 0 | 1 | 1 |
| Disable 6to4 interfaces | 0 | 0 | 0 | 0 |
| Disable Isatap interfaces | 0 | 0 | 0 | 0 |
| Disable Teredo interfaces | 0 | 0 | 0 | 0 |
| Disable native interfaces (also PPP) | 0 | 1 | 0 | 1 |
| Prefer IPv4 in default prefix policy. | 1 | 0 | 0 | 0 |
| Disable CP interfaces | 0 | 0 | 0 | 0 |
| Disable IP-TLS interfaces | 0 | 0 | 0 | 0 |
| Binary | 0010 0000 | 0001 0000 | 0000 0001 | 0001 0001 |
| Hexadecimal | 0x20 | 0x10 | 0x01 | 0x11 |
Using the network properties GUI to disable IPv6 is not supported
This registry value doesn't affect the state of the following check box. Even if the registry key is set to disable IPv6, the check box in the Networking tab for each interface can be selected. This is an expected behavior.
Reference
For more information about RFC 3484, see Default Address Selection for Internet Protocol version 6 (IPv6).
For more information about how to set IPv4 precedence over IPv6, see Using SIO_ADDRESS_LIST_SORT.
For information about RFC 4291, see IP Version 6 Addressing Architecture.
For more information about the related issues, see the articles below:
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- Example 1: On Domain Controllers, you might run into where LDAP over UDP 389 will stop working.See How to use Portqry to troubleshoot Active Directory connectivity issues
- Example 2: Exchange Server 2010, you might run into problems where Exchange will stop working.See Arguments against disabling IPv6 and Disabling IPv6 And Exchange – Going All The Way.
- Example 3: Failover ClustersSee What is a Microsoft Failover Cluster Virtual Adapter anyway? and Failover Clustering and IPv6 in Windows Server 2012 R2.
Tools to help with network trace: Microsoft Network Monitor 3.4 (archive)
Warning
Netmon 3.4 isn't compatible with Windows Server 2012 or newer OS when LBFO NIC teaming is enabled. Use Message Analyzer instead.