# OpenVPN from Linux to IPFire

**URL:** <https://community.ipfire.org/t/openvpn-from-linux-to-ipfire/4780>\
**Category:** OpenVPN\
**Created:** [7 March 2021 08:21 UTC](https://community.ipfire.org/t/openvpn-from-linux-to-ipfire/4780 "2021-03-07T08:21:33Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![zargano](https://community.ipfire.org/user_avatar/community.ipfire.org/zargano/32/268_2.png) [@zargano](https://community.ipfire.org/u/zargano)\
**Post date:** [7 March 2021 08:21 UTC](https://community.ipfire.org/t/openvpn-from-linux-to-ipfire/4780/1 "2021-03-07T08:21:33Z")

</div>

I am migrating from Windows to Linux desktop since a while. One of the last things are to complete by setting up OpenVPN tunnels to IPFire. Using them under Windows with OpenVPN 2.4 client worked flawlessly without trouble.

I am using Debian with Cinnamon, making use of the Gnome Networkmanager. After installing OpenVPN by _sudo apt install network-manager-openvpn-gnome_ , I was principally able to setup an OpenVPN tunnel, but I stumbled though.

When setting up my first OpenVPN connection, I got the error message (original German message) “Konfigurationsfehler: Argument 1 für \>\>mssfix\<\< ist ungültig. Eine Zahl wird erwartet.”, translation “configuration error: argument 1 for \>\>mssfix\<\< is invalid. A number is expected.”

Looking into the related ovpn file generated by IPFire, I do find a number, which is “0”. This is a number! Reading the official OpenVPN documentation, I decided to delete this parameter line from the file. And it seems to work!

A couple of questions…

- Comparing older configuration files with the one used for testing under Linux, I found that the option _mssfix_ is not available in older configuration files. So why was this parameter added?
- Why is the mssfix parameter set to 0 by IPFire? Reading the documentation, this does not make sense with me.
- Should I keep the configuration file without the mssfix parameter?

Thanks, zargano

---

<div class="post-metadata">

**Author:** ![ummeegge](https://community.ipfire.org/user_avatar/community.ipfire.org/ummeegge/32/16602_2.png) [@ummeegge](https://community.ipfire.org/u/ummeegge)\
**Post date:** [7 March 2021 08:51 UTC](https://community.ipfire.org/t/openvpn-from-linux-to-ipfire/4780/2 "2021-03-07T08:51:42Z")

</div>

Hello zargano,  
you can find the patch but also an explanation with this settings here → [git.ipfire.org Git - ipfire-2.x.git/commit](https://git.ipfire.org/?p=ipfire-2.x.git;a=commit;h=d6989b4b0b42937485f5008cda6cdd730275f1ec) .

–mssfix can be disabled with the value 0. It seems that the network-manager is unable to handle this even OpenVPN does provide it. If --mssfix and --fragment are disabled, the MTU value from the global settings will be used.

Best,

Erik

---

<div class="post-metadata">

**Author:** ![zargano](https://community.ipfire.org/user_avatar/community.ipfire.org/zargano/32/268_2.png) [@zargano](https://community.ipfire.org/u/zargano)\
**Post date:** [7 March 2021 10:34 UTC](https://community.ipfire.org/t/openvpn-from-linux-to-ipfire/4780/3 "2021-03-07T10:34:15Z")

</div>

Hi ummegge,

> [@ummeegge](#):
>
> –mssfix can be disabled with the value 0

I did not get this from the documentation. Thanks also for the link to explain the background. I conclude that I can safely delete this line, as long I do not experience performance issues. Since I am using OpenVPN to primarily manage resources behind IPFire, I do not see any problem at all even if I got stuck with a limited throughput in the order of 100 MBit/s.

Best, zargano