OpenVPN Support Forum

Hi,
i'd like an help by tuning up the openvpn connection.During test I am connecting to network without openvpn about 2.5Mb/s download speed, but as soon as I connect to my openvpn server and traffic goes through vpn connection the connection drops down to download speed around 0,50 Mb/s. I am usign => server side: tap0,bridge. the connection where the server is located has download speed 11Mb/s ... any idea what could cause the rapid drop of connection speed?

thanks

hi
does anyone has some clue about this issue?
thx

Greetings,

Yes. I have one.

Bridging is a very cool function of openvpn. There are several situations where it has been a required configuration due to network protocol constraints. It also provides an easy way to integrate roaming users into office LANs. That being said, there is a downside to using it in bridged mode: the broadcast domain. Your bridged client is going to "see" and respond to any broadcasts or multicasts on the remote LAN. This can be good in that it allows your client system to participate as if it was actually there, but a network with more than a few windows hosts can generate a lot of these kinds of packets.

This problem can also be exacerbated when the client is connected to an asymmetrical broadband connection. If your upstream bandwidth is significantly lower than your downstream, your system will be receiving many more broadcasts than it is able to respond to immediately. This will cause things to que up and clog the upstream to a certain extent causing degradation of your downstream performance.

To start troubleshooting this, I would suggest downloading a packet analyzer such as wireshark to get an idea of what sort of remote LAN traffic is actually reaching your client.

A solution to this would be to reconfigure your openvpn server in point-to-point mode rather than providing a bridged connection. For Windows file sharing, you will need to have a designated WINS server to provide network browsing or you can connect by either a host name or IP address. It's less convenient but the performance is worth it.

Regards,
Stephen

Thanks a lot for closer look, it helped a lot especaily I am realy using ADSL linka and the gap between upstrem and downstream is hight too. First I'll start with troubleshooting of this particular network.
thanks a lot.

have a great holiday
m

Fantastic. Let me know how it goes.

-Stephen