OpenVPN Support Forum

Hi all,
I have an OpenVPN Server installed on CentOS.
I have a Sierra Airlink LS300 client (192.160.1.254) connected to the server.
I have comp-lzo configured on the client and on the server.
The VPN conecction between server and client appears as CONNECTED, but i can´t ping from server to client.
The log does not show any highlighted errors. Continuously displays the warning "Bad LZO decompression header byte: 0"
Does anyone know what the reason may be?
The OpenVPN Server version is 2.4.9.
The OpenVPN client version (Sierra Airlink LS300 with ALEOS 4.4.9) is 2.3.17
Thank you very much.

Incompatible compression settings...

viewtopic.php?f=30&t=22603

OK thanks.
So it is not possible to communicate a client with version 2.3.17 with a server with version 2.4.9?
The VPN appears as connected, but I cannot PING from the server to the client.
To be able to do it I have to use an old version of Openvpn on the server?

OpenVPN 2.4 should be compatible with 2.3

OpenVPN recommend that you do not use compression on a VPN due to:
https://community.openvpn.net/openvpn/wiki/VORACLE

You obviously have not used the correct settings..

OK, thank you very much for your help!
But if I don´t use compression, that error is shown in the logfile:

IP packet with unknown IP version=0

Hello,

I was able to find a solution for the compression error.
My VPN goes through two routers interconnected by Wireguard, the 1st router seems to poorly transfer packets to the 2nd router via the VPN.
Because when I disabled compression I had other errors.

To solve the problem I put a low value in the tunnel MTU.
So I removed the options: mssfix and fragment 1500. To replace them with: tun-mtu 1300.

The router still has: iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
to maximize outgoing packets...

So I no longer have any compression problems.

However, be careful with LZO compression, see:
https://community.openvpn.net/openvpn/w ... U_7jJEQYs0

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