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OpenVPN MAC

Posted: Tue Jul 25, 2017 12:42 pm
by roxy
Hi, we have Virtual Hub configured with Virtual DHCP Server enabled. Several OpenVPN connecting clients change IP before DHCP lease time expires (we used standard 7200 seconds lease time as now). Analysing logs we see different OpenVPN Client having same MAC address and we see also same client connecting to VPN server in different moment with different MAC Address. MAC address are of class like CA-BF-1E-42-XX-XX.

Is softether creating these MAC Addresses on behalf of OpenVPN clients ? why we find duplicated MAC address and so different IP before DHCP lease time expires ?

Best regards

Re: OpenVPN MAC

Posted: Thu Aug 03, 2017 6:18 am
by thisjun
SoftEther VPN generate MAC address from machine name, virtual hub name and session unique ID.
https://github.com/SoftEtherVPN/SoftEth ... on.c#L2340

If you want to keep MAC address on client, please use tap mode OpenVPN.

Re: OpenVPN MAC

Posted: Thu Aug 10, 2017 1:13 pm
by roxy
I do not know where, if upper case conversion or hashing, but MAC address in some point is not uniquely assigned to every DIFFERENTE combination of:

machine name
virtual hub name
session unique ID

As we get same MAC for 2 different machine for 2 different sessions on the same virtual hub.

tap is not an option on limited linux set-top box or smartphone...

Re: OpenVPN MAC

Posted: Thu Sep 07, 2017 7:31 am
by thisjun
'machine name' is server's host name.
If the VPN server restarted, MAC address will conflict with previous one.

Re: OpenVPN MAC

Posted: Thu Sep 14, 2017 7:50 pm
by roxy
There are MAC address conflict also if no restart happen, probably session id are not managed to be unique in long time intervals, so if one client disconnect and a new client connect nre client get session id of previous client, and so MAC address. It should be sufficent to manage session id to avoid reuse in shot time intervals or somthing like this

Re: OpenVPN MAC

Posted: Tue Oct 17, 2017 4:58 am
by thisjun
Session ID includes a serial number of session since the virtual hub is enabled.
So, multiple session don't have a same MAC address.
Did you turn off the virtual hub?

Re: OpenVPN MAC

Posted: Wed Oct 18, 2017 2:13 pm
by roxy
Turn off ? what do you mean for "turn off" a virtual hub ?
Virtual Hub is Online if you mean this

Re: OpenVPN MAC

Posted: Wed Nov 01, 2017 6:42 am
by thisjun
Did you use OpenVPN tap mode?

Re: OpenVPN MAC

Posted: Tue Dec 19, 2017 12:21 pm
by roxy
tun mode

Re: OpenVPN MAC

Posted: Fri Jan 05, 2018 5:14 am
by thisjun
I would like to know reproduction condition.
Could you upload log files?

Re: OpenVPN MAC

Posted: Thu Jan 11, 2018 12:13 pm
by roxy
To be more robust we developed our software to get id from devices to distinguish also if different devices be using some IP so we cannot reproduce with easy the issue. If we can in the near future reproduce I'll send you log file.

Re: OpenVPN MAC

Posted: Thu Jan 25, 2018 5:35 am
by thisjun
OpenVPN protocol doesn't have function that send device ID.