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Virtual Private Networking
Egy virtuális magánhálózatba hálózati kártya segítségével hívhat be, ugyanúgy, mint ahogyan egy hagyományos távoli kiszolgálóhoz modem segítségével kapcsolódik.

About VPN connections
A VPN connection is almost like someone installing a second network card in your computer. Being connected to the VPN means that your computer has two “network cables” that it can talk through, and two identities (one for each network). The “vpn cable” on the client machine connects to the back of the server machine (in a TUN network), or into the same hub that the server machine is plugged into (in a TAP network)

This is what a TAP network could look like:
(In this instance your ifconfig line would be in the 192.168.1.x subnet, and would be careful not to assign any ip addresses that the cable/dsl router on your server network might assign. or drop the line and have the cable/dsl router field all requests from machines on the vpn.)

Server machine:
  BRIDGED network (both cards have the same identity): 192.168.1.2
Client machine
 normal network: 192.168.0.2
 vpn network: 192.168.1.3 (same subnet as server, different address)

This is what a TUN network could look like:
(In this instance you should be using a tun-style network.)

Server machine:
 normal network: 192.168.1.2
 vpn network: 192.168.3.1
Client machine:
 normal network: 192.168.0.2
 vpn network: 192.168.3.3 

Ethernet network bridge
Ethernet bridging essentially involves combining an ethernet interface with one or more virtual TAP interfaces and bridging them together under the umbrella of a single bridge interface. Ethernet bridges represent the software analog to a physical ethernet switch. The ethernet bridge can be thought of as a kind of software switch which can be used to connect multiple ethernet interfaces (either physical or virtual) on a single machine while sharing a single IP subnet.

By bridging a physical ethernet NIC with an OpenVPN-driven TAP interface at two separate locations, it is possible to logically merge both ethernet networks, as if they were a single ethernet subnet.