Slow connection to internet via SoftEther VPN on VPS

[neock]

Hi all,

I used a KVM VPS in Singapore with Debian 7.5 x86 to create a private VPN by using SoftEther.
Build from scratch, and with the guidelines I can find from Google, it works.

However only for the first few seconds.

The symptom is that each time I manage to establish a connection between client and the server by L2TP and using Windows 7's built in VPN connection, the first few seconds everything works just fine. I can open every blocked website literally in a blink of eye. But after that first few seconds, the network performance goes poor and the connection speed drops dramatically. Eventually, I can't access to any webpage or the internet at all. However the connection with VPN is still established and not disconnected.

Well, because it's a KVM based VPS, that I can't enable and use promiscuous mode to create local bridge mode. So SecureNAT has to be used.

And yes, I tested VPS's connection speed, it's bandwidth is right at its maximum capacity of 10Mb.
And yes, by using xl2tpd+openswan, this kind of traditional VPN ways I can get an average DL speed of 800KB/s and UL speed of 1000KB/s.

It's strange and weird that only the first few seconds works pretty well for Softether then it crashed. Don't know why exactly.

Can anyone help me to investigate or provide some hints that I can solve the problem?

Thanks in advanced.

[inten]

What is your VPS provider?

[neock]

inten wrote:
> What is your VPS provider?

Currently is ExpertVM.

However the same problem happened before with DigitalOcean, Vultr, Hostigation and 2Host.

[inten]

We have 4 VMs at DigitalOcean in Singapore and everything runs smoothly. Attach your server config.

Btw, promiscuous mode runs on DigitalOcean's VM good as well.

[inten]

... and one more thing regarding ExpertVM:

No spam, public VPN/proxy, torrent, adult content, IRC, copyrighted material/illegal file sharing, video encoding (ie. oscam) and storage within our network.

Be careful with them.
http://expertvm.com/tos.php

[myopenid]

inten wrote:
> We have 4 VMs at DigitalOcean in Singapore and everything runs smoothly. Attach your
> server config.
>
> Btw, promiscuous mode runs on DigitalOcean's VM good as well.

Can I know what is your setup? I currently have a VPS at DigitalOcean and attempted to create a local bridge between a tap adapter with the virtual hub. I've enabled the necessary configurations, such as the iptables NAT and kernel ip forwarding, but no internet. When I check to see what is going on in the tap adapter with wireshark, it seems that packets from the virtual hub never reached the tap adapter, hence no forwarding or any internet connectivity. It's as if the virtual hub has swallowed the packets.

So what is the problem???

[myopenid]

@neock

secureNAT is very CPU intensive. Whenever you create a lot of TCP connection after surfing for quite a while, it makes the VPS freeze due to 100% CPU usage.

Try running 'top' when the internet slows down to see who's the culprit.