DNS, DynDNS and ipv6

Inhaltsverzeichnis

IPv6 Address#

Check/Test IPs 
> ifconfig
> ip a | grep inet6
> ip -4 addr show
> ip -6 -o addr show dev eth0 scope global
> ping -6 2a02:5a0:4110:f590:fdd3:3e99:1234:9876
> ping -6 www.google.com
> nslookup -6 www.google.com
> sudo traceroute -6 www.google.com

The raspberry may have a random ipv6 to hide target. This can happen with "privacy extensions" enabled via dhcpcd (Dynamic Host Configuration Protocol Client Daemon). But this is not enabled by default, check with
> service dhcpcd status
If "Unit dhcpcd.service could not be found." then the random IP is set from Fritz!Box,
If found, you can disable (not recommended): 

> sudo vi /etc/dhcpcd.conf
> slaac private  # change to "slaac hwaddr"
> sudo service networking restart
see Heimnetz > Netzwerk > YourDevice > Heimnetz > "IPv6-GUA-Temporary"
The official IPv6-GUA (Global Unicast-Address) is another one.
But with dyndns we can use the random/temporary one.

Windows 

> ping -6 www.google.com
> ping -6 2a02:5a0:410f:46f0:51ef:ea06:9875:1234
> nslookup myDevice 192.168.188.1	# for 1. target with 2. nameserver
> nslookup myDevice fd94:725a:490a::d624:ddff:fe70:5c5b
> nslookup -debug -type=any -type=aaaa MyComputer 192.168.188.1
> resolvconf -l
> ipconfig        # see also standard gateway here

Fritzbox
temporary vs permanent/secured ipv6

IP lifetime 

> ip addr show eth0
set lifetime to forever:
> sudo ip addr change 2a02:5a0:4110:f590:6547:1234:9876:ee dev eth0 valid_lft forever preferred_lft forever

Network Manager#

I use a custom DNS server setting, because the fritzbox does not resolve my dynv6 domains (?).
Do not modify file "/etc/resolv.conf". Use network manager instead with "nmcli". 
> systemctl status NetworkManager
> sudo vi /etc/NetworkManager/NetworkManager.conf            # config
> sudo vi /etc/NetworkManager/system-connections/*Wired*     # config
> sudo /etc/init.d/networking restart
> sudo systemctl reload NetworkManager
> sudo systemctl status NetworkManager.service 
> sudo systemctl restart NetworkManager.service 	# log in > journalctl -u NetworkManager.service -b
> sudo nmcli device reapply eth0
> sudo nmcli general
> sudo nmcli general reload dns-full    # flush dns cache
> sudo nmcli -o device show	        # show interfaces settings
> sudo nmcli -p connection show	        # show interface status

#THIS IS NECESSARY
> sudo nmcli con mod "Wired connection 1" ipv4.dns "1.1.1.1,8.8.8.8"                # add cloudflare and google dns
> sudo nmcli con mod "Wired connection 1" ipv4.ignore-auto-dns no                   # this adds "search fritz.box" to get ips at all from frit.box
> sudo nmcli con mod "Wired connection 1" ipv6.ignore-auto-dns yes                  # we skip ipv6 dns
> sudo nmcli c down "Wired connection 1" && sudo nmcli c up "Wired connection 1"    # restart

> sudo nmtui	                                                                    # visual tool for network manager
> sudo nmcli conn up eth0
> sudo nmcli con mod "Wired connection 1" ipv4.dns 10.0.0.1
> sudo nmcli con mod "Wired connection 1" ipv6.dns 2606:4700:4700::1111
> sudo nmcli con mod "Wired connection 1" ipv6.dns-priority 100 ipv4.dns-priority 50
> sudo vi /etc/resolv.conf    # validate settings
> sudo nmcli connection modify help    # help
> nmcli connection modify "Wired connection 1" -ipv6.dns fd94:725a:490a:0:d624:ddff:9867:1234
> nmcli device modify eth0 ipv4.ignore-auto-dns yes                # remove dns nameservers
> sudo nmcli con mod "Wired connection 1" ipv6.ignore-auto-dns no  # remove dns nameservers

Reset 

sudo rm /etc/resolv.conf
sudo systemctl restart NetworkManager

DHCP 

> service --status-all    # check all services
If you see "networking", this seems do be dhclient 
> sudo vi /etc/default/networking    # config
> sudo vi /etc/dhcp/dhclient.conf    # config
> sudo dhclient -v eth0              # renew
> sudo dhclient -6 -r -v eth0        # force renew
> sudo systemctl restart networking  # restart
> sudo ifconfig eth0 down && sudo ifconfig eth0 up

DynDNS#

DynDNS with ddclient#

> sudo apt-get update                               # update repositories
> sudo apt-get install ddclient                     # install
> sudo vi /etc/ddclient.conf                        # config file
> sudo service ddclient restart                     # restart daemon
> sudo rm /var/cache/ddclient/ddclient.cache        # clear IP cache uploaded before (or use -force)
> systemctl status ddclient                         # status check
> journalctl -xeu ddclient                          # log 
> sudo ddclient -query                              # try all common dyndns services
> sudo ddclient -daemon=0 -debug -verbose -noquiet  # start directly with verbose output to analyse

> sudo vi /etc/default/ddclient
> sudo vi /usr/bin/ddclient

With current Raspberry OS (Debian GNU/Linux 12, bookworm) you get ddclient v3.10.0. This could not determine the ipv6 address !
The latest v3.11.2 worked fine, see next.

Install ddclient on your own#

Based on najigram.com 
> sudo apt purge ddclient
> sudo apt install libjson-any-perl libdata-validate-ip-perl libio-socket-ssl-perl
> sudo apt install libtool        # this is missing at najigram.com and solves issues if autogen does not work
> wget https://github.com/ddclient/ddclient/archive/refs/tags/v3.11.2.zip
> unzip v3.11.2.zip
> cd ddclient-3.11.2
> sudo ./autogen
> sudo ./configure --prefix=/usr --sysconfdir=/etc/ddclient --localstatedir=/var
> sudo make
> sudo make VERBOSE=1 check
> sudo make install	
> sudp cp sample-etc_systemd.service /etc/systemd/system/ddclient.service

> sudo vi /etc/ddclient/ddclient.conf

Add below "ssl=no": 

protocol=dyndns2
#use=if, if=eth0
usev6=ipv6, ipv6=eth0
#use=web, web=checkip.dyndns.org,  web-skip=‘Current IP Address’
verbose=yes
daemon=900
#pid=/var/run/ddclient.pid
#mail-failure=msebel20@gmail.com
server=dynv6.com
login=XUsernameX
password=XPasswordX
<your dyndns server name>

Test DynDNS / Error DNS_PROBE_FINISHED_NXDOMAIN#

Note: it is sufficient to register just an ipv6 address with your dyndns provider (AAAA record). You do neither need an ip4 address (A record) nor any other DNS zone entry.
  1. enable a port to forward to your device in your router
  2. test the port forwarding without DNS first, you can call an ipv6 address like this https://[2a02:x205:..]:1234 (https://[ipv6]:port)
  3. test domain name resolution (DNS)
    • Firefox uses its own DNS server (not the OS one) and those worked from scratch, see Settings > Security > DNS over HTTPS > Anbieter (Cloudflare)
    • Windows used the FritzBox to resolve and that did not work (?). I entered a dedicated DNS server at Windows + R > ncpa.cpl > Ethernet > Porperties > Internetprotokoll, Version 4+ 6 > DNS (I used cloudflare and google as alternative, you can search for "DNS server list").
Cloudflare 1.1.1.1 2606:4700:4700::1111
Google 8.8.8.8 or 8.8.4.4 2001:4860:4860::8888 or 2001:4860:4860::8844
Digitalcourage e.V. 46.182.19.48 2a02:2970:1002::18
Digitale Gesellschaft 185.95.218.42 2a05:fc84::42
dismail.de 80.241.218.68 2a02:c205:3001:4558::1 
> ipconfig
> ping -6 2a02:x205:... or serverName
> netsh int ip show address
> route print -6
> arp -a

DNS Cache Lookup / Purge#

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