Multiple VPN simultaneously, result?
Is it possible to use two VPNs simultaneously. F.ex. by having a site to site connection on my router and while using another VPN on the client? If not, what would happen in that case?
To a point and I will first assume you are using commercial routers to do this since consumer routers have strange restrictions sometimes.
Lets for example say you had a VPN over the internet between 2 offices. Then inside those offices you wanted to connect 2 special test labs. You could build a second VPN between the devices in these labs because in theory at least the outer VPN is passing all protocols..key word here is protocols. There would likely be performance issue at some point.
The other one that would likely work but it depends on the provider...you could use a vpn to one of the vpn hosting services from the router and then create a VPN say to your company from your client. It would in effect pass though and appear to originate in the hosting center. Since in the senerio you are not in control of all the pieces it should work but the VPN can be internationally configured to prevent it.
Most other types of VPN for example if you wanted to run 2 vpn from your house at the same time but not running one tunneled inside the other will likely have major issues. Mostly because you only have a single IP and NAT gets in the way a lot. If you were to use SSL/TLS VPN you would be most likley to get it to work since these look like HTTPS sessions.