IPv6: Difference between revisions

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[[Category:networking]]
[[Category:Linux/Unix]]
Testing your IPv6 connection:
;https://ifconfig.co/
:Including CLI-support
;https://ready.chair6.net/
:Nice as simple interface
;https://test-ipv6.com/
Testing website security and connectivity
;https://internet.nl


;https://test-ipv6.com/
Below seems to be broken December 2025
;https://ipv6-test.com/
;https://ipv6-test.com/
:Check your IPv6 configuration
:Check your IPv6 configuration
;http://ipv6-test.com/validate.php
:Check IPv6 support for websites




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<td>FC00::/7</td>
<td>FC00::/7</td>
<td>Unique Local Unicast</td>
<td>Unique Local Unicast</td>
<td>Local Unicast. For intranets, not routed, like IPv4 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16</td>
<td>Local Unicast. For intranets, not routed, like IPv4 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Currently FC00::/8 is undefined, only FD00::/8 is used</td>
</tr>
</tr>
<tr>
<tr>
<td>FE80::/10</td>
<td>FE80::/10</td>
<td>Link Local Unicast</td>
<td>Link Local Unicast</td>
<td>Link Identification, addresses often contain the MAC address. MAC 00:16:3e:31:c4:a0 =&gt; fe80::2<em><strong>16</strong></em>:<em><strong>3e</strong></em>ff:fe<em><strong>31</strong></em>:<em><strong>c4a0</strong></em>/64</td>
<td>Link Identification, addresses can be based on the interface MAC address</td>
</tr>
</tr>
<tr>
<tr>
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</table>
</table>


==Local Unicast (ULA)==
Users were advised to generate a 40 bits Global ID for their intranets but it is unclear if there a valid use case for it[[https://en.wikipedia.org/wiki/Unique_local_address]]. It is advised to calculate the Global Id using a specified procedure to maximize the probability of an unique address.


==Local Unicast==
<strong>[http://tools.ietf.org/html/rfc4193#section-3.2 Local Unicast Address-format]:</strong>
Uses are advised to generate a 40 bits Global ID for their intranets.  It is advised to calculate the Global Id using a specified procedure to maximize the probability of an unique address.
 
[http://tools.ietf.org/html/rfc4193#section-3.2 Local Unicast Address-format]
<table>
<table>
<tr>  
<tr>  
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Locally assigned</td>
Locally assigned</td>
<td>40 bits<br />
<td>40 bits<br />
Randomly generated</td>
User defined</td>
<td>16 bits<br />
<td>16 bits<br />
Local subnet</td>
Local subnet</td>
<td>64 bits<br />
<td>64 bits<br />
From MAC address</td>
Locally assigned or by dhcp</td>
</tr>
</tr>
<tr>
<tr>
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</table>
</table>
The Interface ID is in the so-called &#8216;Modified EUI-64 Format&#8217;. How to go from a MAC address to Modified EUI-64 format is described in appendix A of [href="http://tools.ietf.org/html/rfc4291 RFC 4291].The Routing Advertising Daemon radvd provides &#8216;Stateless Autoconfiguration&#8217; e.g. by assigning IPv6 addresses and routing information to nodes on the LAN.
The Interface ID is in the so-called &#8216;Modified EUI-64 Format&#8217;. How to go from a MAC address to Modified EUI-64 format is described in appendix A of [href="http://tools.ietf.org/html/rfc4291 RFC 4291]. When using ULA prefixes you must have Routing Advertising (radvd) to tell the network it should configure addresses and routes for it
 
==Route Advertisement==
Provides information for &#8216;Stateless Autoconfiguration&#8217; to the local nodes.
 
IPv6 systems can send a Route Solicitation (RS) messages. These are answered by a Route Advertisement (RA) message that tells with prefixes exist and, when needed where the gateway for that prefix is. The client then can configure IPv6 addresses and routes.
 
On linux systems there is the radvd deamon to provide RA.


To advertise there is a ULA prefix in the network put this in /etc/radvd.conf
<syntaxhighlight lang=text>
interface eth0
{
    AdvSendAdvert on;
    AdvDefaultLifetime 0;
    prefix fdxx:xx:xx::/48
    {
    };
};
</syntaxhighlight>


==Disable IPv6 on a system==
==Disable IPv6 on a system==
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;cat /proc/sys/net/ipv6/conf/all/disable_ipv6
;cat /proc/sys/net/ipv6/conf/all/disable_ipv6
:Check if IPv6 has been disabled, then the file as 1, else 0
:Check if IPv6 has been disabled:
:0 => IPv6 is not disabled
:1 => IPv6 is disabled
 
==Check IPv6 autoconfiguration==
;<code>cat /proc/sys/net/ipv6/conf/eth0/autoconf</code>
:0 => autoconf is disabled
:1 => autoconf is enabled
 
==Misc commands==
 
;/sbin/ip -6 addr del <ipv6address>/<prefixlength> dev <interface>
:Remove ipv6 addres from an interface

Latest revision as of 20:32, 4 January 2026

Testing your IPv6 connection:

https://ifconfig.co/
Including CLI-support
https://ready.chair6.net/
Nice as simple interface
https://test-ipv6.com/

Testing website security and connectivity

https://internet.nl

Below seems to be broken December 2025

https://ipv6-test.com/
Check your IPv6 configuration
http://ipv6-test.com/validate.php
Check IPv6 support for websites


Address Assignment

The IPv6 address assignment is handled by IANA. Most important prefixes are:

2000::/3 Global Unicast Global scope
FC00::/7 Unique Local Unicast Local Unicast. For intranets, not routed, like IPv4 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16. Currently FC00::/8 is undefined, only FD00::/8 is used
FE80::/10 Link Local Unicast Link Identification, addresses can be based on the interface MAC address
FF00::/8 Multicast

Local Unicast (ULA)

Users were advised to generate a 40 bits Global ID for their intranets but it is unclear if there a valid use case for it[[1]]. It is advised to calculate the Global Id using a specified procedure to maximize the probability of an unique address.

Local Unicast Address-format:

Prefix L Global ID Subnet ID Interface ID
7 bits
FC00::/7		 1 bit
Locally assigned		 40 bits
User defined		 16 bits
Local subnet		 64 bits
Locally assigned or by dhcp
1111110 1

The Interface ID is in the so-called ‘Modified EUI-64 Format’. How to go from a MAC address to Modified EUI-64 format is described in appendix A of [href="http://tools.ietf.org/html/rfc4291 RFC 4291]. When using ULA prefixes you must have Routing Advertising (radvd) to tell the network it should configure addresses and routes for it

Route Advertisement

Provides information for ‘Stateless Autoconfiguration’ to the local nodes.

IPv6 systems can send a Route Solicitation (RS) messages. These are answered by a Route Advertisement (RA) message that tells with prefixes exist and, when needed where the gateway for that prefix is. The client then can configure IPv6 addresses and routes.

On linux systems there is the radvd deamon to provide RA.

To advertise there is a ULA prefix in the network put this in /etc/radvd.conf 

interface eth0
{
    AdvSendAdvert on;
    AdvDefaultLifetime 0;
    prefix fdxx:xx:xx::/48
    {
    };
};

Disable IPv6 on a system

At the end of /etc/sysctl.conf add: 

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
sysctl -p
Force reload of the kernel parameters as in /etc/sysctl.conf
cat /proc/sys/net/ipv6/conf/all/disable_ipv6
Check if IPv6 has been disabled:
0 => IPv6 is not disabled
1 => IPv6 is disabled

Check IPv6 autoconfiguration

cat /proc/sys/net/ipv6/conf/eth0/autoconf
0 => autoconf is disabled
1 => autoconf is enabled

Misc commands

/sbin/ip -6 addr del <ipv6address>/<prefixlength> dev <interface>
Remove ipv6 addres from an interface
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