Today I am posting what IMOH is a real ugly thing and I think I would not even post an answer for this if I would read it.

I have a raspberry pi working as a VPN GW which it did very nice for 5 days. Now the whole night and till the beginning of workhours everything works fine and the vpn is working, but when the users start to use the connection, the whole ppp connection breaks down.

When the reboot the pi, everything is nice again for lets say 10 minutes to 2 houres and than it breaks down again.

The whole weekend the connection was up and working. I started a download from kernel.org just to get a litle trouble on the wire, but the connection did not break down.

Does anyone have any idea what to do ?

I will now check all the cables
maybe switch the pi
have a look at the system in place

Exactly how many users are using this VPN?
The rasp is not enterprise hardware, hell its not even entry level server hardware, using the rasp for 2-3 users at most is pushing the boundries.

We use it for two user, and i would disagree the we are pushing it to the edge. The pi is only doing the network traffic, no one is really working on the pi.
We have very good experience with openWRT and more then 200 network connections (no VPN).

But i am always thankful for any input and other opinions.

Its the network traffic I am worried about, the rasp doesnt have full Gbit through put because it shares the bus with the USB2.0 interface, meaning the max throughput you can achive is 480Mbit at best (that is enough for 2-3 people granted) but keeping the connections reliable and alive on a USB controller is another matter. You can try to see if there are any driver options you can play around with, but I would be very surprised if you got this to work without having to restart it through out the day.

Also what is the connection timeout on openvpn service? Setting the timeout lower to kick users off might free up resources the downside is they would have to reconnect every x amount of hours.

Ok, i got that.
I did not think about the network traffic, as we only use it for 2 users having a citrix-connection to the computing center.

Anyone an idea what hardware to use, for more than 2 users ?

Let`s say 20-30. I am also thinking about a remoteconnection for other branches.

So i tested the throuput with a download from kernel.org.

Got 901KB/s.

For 20-30 users you are going into Cisco ASA and Juniper areas of expertise.
Not to say they can't be done with off the self parts it can, just not as relibly these products were made to do these things.

If you really want to go down the hinz 57 route, then 4 GB ram, intel core duo and 2-4 nic's call trunked together as one big pipe going into a 24-48 port switch.
That should be good enough for running just a VPN (openvpn) and holding the encryption tunnel stable.

Yes with compression, without compression your getting 600Kb/sec (600/3)= 200K (if all 3 users are on,thats if you hit the max throughput)

But what would be an alternative ?
Something like the Pi with 2 nics ?