User:Vazhnov/Knowledge Base:IPv6 only

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With default settings from Gentoo handbook, it is easy to work with dualstack IPv4 + IPv6, if corresponding network settings are made.

This how-to describes how to work with IPv6 only, without IPv4 address on the network interface.

Preparations

Internet connection

Check IPv6 connection works properly:

user $ping -c3 2600::
PING 2600::(2600::) 56 data bytes
64 bytes from 2600::: icmp_seq=1 ttl=50 time=135 ms
64 bytes from 2600::: icmp_seq=2 ttl=50 time=138 ms
64 bytes from 2600::: icmp_seq=3 ttl=50 time=135 ms

--- 2600:: ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2003ms
rtt min/avg/max/mdev = 135.092/136.223/138.327/1.489 ms

Check the router answer with ICMPv6 router Discovery tool (from net-misc/ndisc6):

user $rdisc6 eth0
Soliciting ff02::2 (ff02::2) on eth0...

Hop limit                 :           64 (      0x40)
Stateful address conf.    :          Yes
Stateful other conf.      :          Yes
Mobile home agent         :           No
Router preference         :       medium
Neighbor discovery proxy  :           No
Router lifetime           :         1800 (0x00000708) seconds
Reachable time            :  unspecified (0x00000000)
Retransmit time           :  unspecified (0x00000000)
 Source link-layer address: D8:58:D7:01:XX:XX
 MTU                      :         1480 bytes (valid)
 Prefix                   : 2001:XXX:XX:XXX::/64
  On-link                 :          Yes
  Autonomous address conf.:          Yes
  Valid time              :     infinite (0xffffffff)
  Pref. time              :     infinite (0xffffffff)
 Prefix                   : fd84:5168:xxxx::/64
  On-link                 :          Yes
  Autonomous address conf.:          Yes
  Valid time              :     infinite (0xffffffff)
  Pref. time              :     infinite (0xffffffff)
 Route                    : fd84:5168:xxxx::/48
  Route preference        :       medium
  Route lifetime          :         1800 (0x00000708) seconds
 Recursive DNS server     : fd84:5168:xxxx::1
  DNS server lifetime     :         1800 (0x00000708) seconds
 from fe80::da58:d7ff:xxxx:xxxx

Gentoo mirrors

Check if mirror(s) are accessible by IPv6.

Get GENTOO_MIRRORS:

user $portageq gentoo_mirrors
http://mirror.eu.oneandone.net/linux/distributions/gentoo/gentoo/ http://distfiles.gentoo.org

Check: both 

HTTP/1.1 200 OK
Server: nginx/1.6.2
Date: Sat, 01 Jan 2022 19:42:12 GMT
Content-Type: text/html
Connection: keep-alive

HTTP/1.1 200 OK
Date: Sat, 01 Jan 2022 19:44:19 GMT
Content-Type: text/html;charset=UTF-8
Connection: keep-alive
alt-svc: quic="138.199.17.176:443"; ma=2592000; v="44,43,39"
…

Get rsync mirrors:

user $portageq repositories_configuration /|grep 'sync-uri'
sync-uri = rsync://rsync.de.gentoo.org/gentoo-portage/
user $rsync -6 rsync.de.gentoo.org::
rsync8.de.gentoo.org

  IPv4:    46.101.221.22
  IPv6:    2a03:b0c0:3:d0::c3:f001 
  Contact: rsync@moonitor.org

gentoo-portage 	Gentoo Linux Portage tree mirror

Network interface

no GUI

Example:

FILE /etc/conf.d/net
config_eth0="null"

GUI

NetworkManager settings:

  • IPv4 settings tab: method = disabled,
  • IPv6 settings tab: method = automatic.

DNS settings

no GUI

net-misc/ndisc6 is needed to update DNS settings in /etc/resolv.conf by information from the router via RDNSS (router advertisement DNS).

GUI

NetworkManager automatically fill /etc/resolv.conf with correct information.

Zeroconf/Avahi

If you use .local addresses in local network, then you have to adjust Zeroconf settings.

By some reason, Zeroconf client in Linux is configured to be IPv4-only by default (mdns4_minimal in /etc/nsswitch.conf).

Check how it works before change, you need some real hostname of device in local network:

user $getent hosts some-real-hostname.local

Replace IPv4-only mdns4_minimal by IPv6-only mdns6_minimal:

root #sed -i -- s/mdns4_minimal/mdns6_minimal/g /etc/nsswitch.conf
Important
Don't use dualstack mdns_minimal parameter in /etc/nsswitch.conf because it causes some programs (like OpenSSH client) to wait for seconds for IPv4 resolution, and then start IPv6 resolution. See Please update/clarify/justify recommendations for IPv4-only vs. any-protocol and libnss-mdns: Replace mdns4* by mdns* in /etc/nsswitch.conf for more details.

No need to restart anything. Run the test again:

user $getent hosts some-real-hostname.local

Also, check configs of all devices in local network:

FILE /etc/avahi/avahi-daemon.conf
[server]
use-ipv4=yes
use-ipv6=yes

Apply

Reboot the OS?

root #shutdown -r now

NAT64 and DNS64

These services are needed to reach IPv4-only resources from IPv6-only workstation.

More information: Wikipedia:NAT64, Wikipedia:IPv6 transition mechanism#DNS64.

It is possible to setup your own NAT64 and DNS64 stack (if your router has public IPv4 address?).

Also, it is possible to use some public service, for example https://www.trex.fi/2011/dns64.html :

FILE /etc/resolv.conf
# dns64.trex.fi
nameserver 2001:67c:2b0::4
nameserver 2001:67c:2b0::6

How to check

Check OS updating work.

Check web-sites in the web-browser.

Check IM software works.

Known issues

NFS shares mount from fstab

Compared to config_eth0="auto" or config_eth0="dhcp", the functionality of auto-mounting network file systems will be lost (netmount service of Nfs-utils?).

dhclient overwrites resolv.conf

If you run

root #dhclient

to receive IPv4 once, configuration /etc/resolv.conf will be overwritten.

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