A mac computer (OSX Mavericks) is connected to a TP-Link router via WiFi, as well as a number of other devices. The TP-Link cable router (no ADSL modem), is not connected to a WAN. The mac computer has access to the internet via USB 3G modem. I would like, if possible, to offer my mac's internet connection to the LAN and have the mac act as the gateway of the LAN.

In short, replace Internet access of the router through WAN with mac's access to internet through USB 3G modem.

USB3G -- Mac -- Router -- Device1, Device2, etc

i.e. give internet access to Device1, through Mac's internet access of USB3G. It has to pass through the router, therefore using OSX's internet sharing is not an option.


  • There is an option for Internet Sharing in the System Preferences pane Sharing. You should be able to set up what connection you want to share to another interface. – Hoshts Oct 21 '15 at 22:46
  • Using Internet Sharing will create an Ad-Hoc wifi network on the Mac, and it will lose connectivity with the router. The point is so that every device connected to the router can use the Mac's internet access through the router. Hence me trying to use the Mac as the router's LAN gateway (virtual WAN). – tidytuna Oct 21 '15 at 23:00

Internet Sharing

Open System Preferences, under the Sharing pane, you can configure Internet Sharing:

enter image description here

  1. Share your connection from: select your 3G USB modem

  2. To computers using: Select the interface that your router is attached to (I assume ethernet0)

With that set, you will need to configure your router to use the iMac as the gateway (by plugging it into the WAN port or somehow configuring that in the router's UI).

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