ipv6 connexion fail - ipv4 OK

Daniel tech at tootai.net
Fri Aug 27 17:16:21 UTC 2021

Hi ROman

Le 27/08/2021 à 18:14, Roman Mamedov a écrit :
> On Thu, 26 Aug 2021 13:14:00 +0200
> Daniel <tech at tootai.net> wrote:
>> Correction
>> Le 25/08/2021 à 17:25, Daniel a écrit :
>>> Hi list,
>>> I setup wireguard on a server running Debian 11 and get it to work with
>>> 2 clients (Debian 11 and Ubuntu 20.04). Clients and server are on
>>> separate networks, one client behind a FW the other direct on Internet,
>>> no FW at all (VPS).
>>> With this setup and ipv4 connection to the public IP of the server,
>>> everything is working as expected, ipv4 as well as ipv6 are passing
>>> smoothly.
>>> Now I want to connect using the ipv6 address of the wg interface as both
>>> clients and server have ULA ipv6.
>> Here is GUA to read.
>>> This fail, wg show that connection is
>>> established but VPN is not usable. It's not a FW problem as I can ssh to
>>> the ipv6 address, as well as a netcat test from/to server IP -from each
>>> client- on an UDP port is working properly. Also,
>>> net.ipv6.conf.all.forwarding=1 is activated in sysctl.conf
>>> All network stuff is done in /etc/network/interfaces which call the
>>> config file. The ipv6 address of the server is affected _to the
>>> wireguard interface_ (in ipv4 it's another interface who take care of
>>> the public address)
>>> Server version is wireguard-tools v1.0.20210223.
>>> If someone have any hint, thanks to share ;)
> IPv6 requires the in-WG MTU to be 20 bytes less than when running over IPv4.
> Try reducing it accordingly.

Tried 1400, 1396 and 1392, problem stay.

Thanks for your help


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