i want to know how a LINUX VPN server delivers a reply packet to a VPN client when the packet's private source IP address (assigned by the VPN server) is replaced with a public address(i access the internet via the VPN tunnel).When the reply packet arrives at the VPN server, the packet's destination address will be the VPN server's public address.So how can the VPN server knows the packet is destined for VPN client and routes it properly. Thanks in advance!

  • Because the NAT device at the destination network keeps a NAT table, and when it translates it back, the VPN server responds on the ARP for the IP address and then the VPN server then tunnels it back to the VPN client. The same as any device on your network contacts the VPN client really. – Mark Henderson May 27 '15 at 1:32
  • thanks! i've got further understanding by reading this article. firewall.cx/networking-topics/network-address-translation-nat/… – benson May 27 '15 at 2:18

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