"Normal" packet loss of ping over OpenVPN?

slu

We have some (~ 40) OpenVPN Connections over a APU board and sometimes a packet lost (VNC connection interrupt).

Normally the connection is complete idle and only on connection has some load.
I'am really unsure where to start, try today another internet connection, same issue.
Often 1000 packets without a lost, sometimes the lost start after ~ 130 packets.

Is the APU hardware to small?
Load average 0.08, 0.06, 0.07 look ok to me.

slu

--- 192.168.131.1 ping statistics ---
1390 packets transmitted, 1389 packets received, 0.1% packet loss
round-trip min/avg/max/stddev = 143.982/152.785/432.330/17.720 ms

Is this a normal loss?

cmb

"Normal" would be close to whatever your loss is outside the tunnel. Sub-0.1% loss is normal for some Internet connections, especially for destinations that are far away from you. 0.1% packet loss wouldn't cause VNC connections to be interrupted, and wouldn't likely be noticeable at all. If you have longer periods of loss, or more than 1 in 1400 packets lost, then you might have an issue there. But that won't cause VNC connection drops.

slu

@cmb:

"Normal" would be close to whatever your loss is outside the tunnel. Sub-0.1% loss is normal for some Internet connections, especially for destinations that are far away from you.

I have one destination ~ 8000km away with no loss in 500 pings.
Another destination ~ 1000km away loss packet after ~ 130 pings, look like there is nothing I can do with a openvpn setting, or?

@cmb:

But that won't cause VNC connection drops.

Yes, if the VNC connection drops I can not see a ping for more than 2 seconds.
OpenVPN log show only:

openvpn[32381]: ca_name/xx.xx.xx.xx:1194 send_push_reply(): safe_cap=940

cmb

In that case, you're more than likely encountering loss on the outside of the tunnel. Run a ping outside the tunnel as well, to the public IP of the OpenVPN server, and see how the loss compares to that inside the tunnel.

slu

No loss from pfSense to WAN IP (OpenVPN Client) and from router to OpenVPN client nic.
For some reason the UDP OpenVPN tunnel loss the packets. :-[

slu

There are a lot of this errors on the client side:

TLS Error: local/remote TLS keys are out of sync

This is the reason of the ping loss, but don't find out why the keys out of sync.

slu

Maybe it is a MTU problem, try a smaller MTU on the server side (can not modify the client).
Is this warning a problem?

WARNING: 'link-mtu' is used inconsistently, local='link-mtu 1300', remote='link-mtu 1542'