NAT & Double NAT


There are 4 billion IP addresses are available in IPv4 (32 bits) network. If each person connect to the internet using individual IP address, the current IP addresses in IPv4 (4,294,967,296) is not enough. Network Address Translation (NAT) concept was introduced to solved this IP address issue.  The router get only one public IP address from ISP and all other connected devices gets the private IP address, it usually start with 192.168.0 or 10.0.0.  NAT converts all private IP address request and send outside the world using one public IP address.  With this, a home or an organization needs only one public address to connect the internet. Router are distributing private IP addresses using DHCP function.


Double NAT means multiple devices on the network are performing NAT functions. Example for this is, WiFi Routers are connected with the ISP Modem / Routers. It won’t prevent you to connect the internet, but sometimes it will create issues for VPN connections, accessing SSL websites, online games, and accessing other private network.

Solutions for Double NAT:

  • Enable Bridge mode in wireless router
    • Login to wireless router admin page in web-browser
    • Settings page, enable the bridge mode or disbale NAT and DHCP functions.
  • Set wireless router in modem’s DMZ
    • Login to wireless router admin page and find the WAN IP Address
    • Login to modem and go to DMZ settings.
    • Add wireless router, WAN IP address in DMZ settings.
  • Setup PPPoE between modem and wireless router
    • set PPPoE in wireless router.
    • PPPoE will bypass the NAT in the modem.

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