Frequently Asked Questions

An established VPN connection causes your system to obtain a new virtual network interface. All traffic sent over this network interface arrives at the other side of the VPN tunnel and all traffic sent back arrives at that interface. Like any interface, this interface needs an IP address to be functional. Either the VPN gateway assigns you an IP address using a client provisioning method or you need to assign one to yourself. In the later case, the IP address of the field "Local Address" is used as IP address for the virtual interface or, in case that field is left blank, the IP address of your primary network interface is used, since it is allowed to assign the same IP address to more than one interface. Basically you are free to assign yourself any IP address you like, albeit it should usually be a private IP address and you need to make sure it does not conflict with the IP address other VPN users are using. There is just one exception to that rule: Usually you cannot assign yourself an IP address that lies within the remote network itself, as if you do, the connection may come up but it cannot be used productively. The reason for that is very simple. If you assign yourself an IP address from within the remote network, servers and hosts at the remote side will think you are also a local host whenever they see a packet from you. So they will try to contact you directly over the local network but that cannot work, as in fact, you are not a local host. The only way to contact you is by going over the VPN gateway and remote hosts won't try to do that for hosts they consider local. To make such a configuration possible, the VPN gateway must support ARP Proxying and most gateways will only support that, if they themselves have assigned the IP address to the client. If you assign IP addresses using a form of client provisioning, then some gateways will allow you to assign IP addresses that lie within one of the remote networks and the connection will wok normally.