Help with online.net ipv6 / ubuntu 16.04

allXunder

Hi everybody! I suffer from the following problem - not long ago my Ubuntu 16.04 server at online.net started to loose ipv6 leases. I found a related bug at launchpad ( https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/1551351 but even though it seems to be closed as resolved (and installed software version should have fix applied) I suffer from that issue.
Online.net support did not give me much information we only found that the problem is on my side.
ISC dhcp-client support did not helped me eather.
Any ipv6 professional help will be highly appreciated.
At least point me to a place I can dig to.
What I found myself is that at a time dhcp lease should be recieved - link is not ready (but it somehow recieves it and it lasts for about 15 minutes than it falls away).

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Jun 06 14:23:28 sd-67550 dhclient[874]: Internet Systems Consortium DHCP Client 4.3.3
Jun 06 14:23:28 sd-67550 sh[857]: Internet Systems Consortium DHCP Client 4.3.3
Jun 06 14:23:28 sd-67550 sh[857]: Copyright 2004-2015 Internet Systems Consortium.
Jun 06 14:23:28 sd-67550 sh[857]: All rights reserved.
Jun 06 14:23:28 sd-67550 sh[857]: For info, please visit https://www.isc.org/software/dhcp/
Jun 06 14:23:28 sd-67550 dhclient[874]: Copyright 2004-2015 Internet Systems Consortium.
Jun 06 14:23:28 sd-67550 dhclient[874]: All rights reserved.
Jun 06 14:23:28 sd-67550 dhclient[874]: For info, please visit https://www.isc.org/software/dhcp/
Jun 06 14:23:28 sd-67550 dhclient[874]:
Jun 06 14:23:28 sd-67550 kernel: IPv6: ADDRCONF(NETDEV_UP): enp1s0f0: link is not ready

Jun 06 14:23:31 sd-67550 kernel: IPv6: ADDRCONF(NETDEV_CHANGE): enp1s0f0: link becomes ready

rm_

How about trying a different DHCPv6 client, namely WIDE DHCPv6. That was the one which worked best for me.

Shot2

I use vanilla Ubuntu 17.04, but anyway here is how I got stable IPv6 on a dedibox (external interface is named eno1 here, I redacted IP and MAC addresses):

• No change to sysctl params whatsoever

• The relevant /etc/network/interfaces part:

# The primary network interface auto eno1 iface eno1 inet dhcp iface eno1 inet6 static address 2001:bc8:xxxx:xxxx::1 netmask 56 autoconf 0 pre-up /sbin/dhclient -cf /etc/dhcp/dhclient6.conf -6 -P eno1 pre-down /sbin/dhclient -x -pf /var/run/dhclient6.pid

• Created by hand this /etc/dhcp/dhclient6.conf file:

# For Online.net dedibox IPv6 subnet interface "eno1" { send dhcp6.client-id 00:00:00:00:12:34:56:ab:cd:ef; request; }
(use whatever DUID your personal IPv6 subnet has, find it in Online's console)

• Also make sure you don't block dhcp exchanges (incoming udp from port 547 to your port 546 of interface eno1) with your firewall

Then reboot. After a short while, IPv6 comes up, DHCPv6 leases should get renewed twice a day.

allXunder

@rm_ will try it - maybe it will help, thanks!
@Shot2 - mine settings are the same, and it works at start, but only for 15 minutes or so.