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If I use a 3G USB modem with a SIM card on my Linux machine, do I get the IP address assigned by the carrier just as my phone when it uses the same SIM card, or do I get a different IP address (as it happens with USB tethering: the phone gets the IP address assigned by the carrier, PC gets a different address as in a local network with the phone only)?

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Whatever's talking directly (at layer three) to the provider gets the address the provider assigns, which is usually global. Though, if you connect a Linux box directly to a modem, then that's it.

  • Is it the same on an Android devide? I mean it's the same if I put the SIM card inside or if I use a usb (usb on the go) modem with that SIM card? – the structure Aug 19 '15 at 20:40
  • if it's really just a modem, then it doesn't do anything at the IP layer. It won't have an IP address; it'll just shunt IP packets back and forth between the phone and the upstream router. The phone'll request an IP, the upstream router will issue one, and the modem basically just translates between the two. note that a lot of things are referred to as ““router””s or ““modem””s, but are actually modems, routers, switches, and usually WAPs, all rolled into one (I call these /combo boxes). if yours is one of these, then /it/ will request an IP from the provider and do NAT to its clients. – VaTo Aug 19 '15 at 20:44
  • ...which is why I hate the loose terminology that some manufacturers use today. – Jonathon Reinhart Aug 19 '15 at 21:12

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