A security gateway provides a secure connection among one or more networks and a protected resource network. One of the local networks may be connected to the remote private network via a VPN IPsec tunnel. The networks may be local networks that share resources without compromising the security of the protected resource network. The local networks may have access to an untrusted network such as the Internet, sharing a single connection through the security gateway. Dynamic source network address translation is used to permit access from the network connected to the protected resource network to other, less trusted networks while concealing the actual IP addresses of hosts within that network.