A gateway is an entry to another network, usually router device play the gateway function as well.

  1. Is it possible that router delegate the gateway function to a device in the LAN and make it to be the gateway? Then the appointed device takes all the responsibility to communicate with the outside world.

  2. If a router loses the gateway function, can it still be caller router? will it become a switch?

  3. In which business scenario, this design will be chosen?

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  • This diagram looks like a NAT gateway in aws.
    – Ryan Lyu
    Commented Apr 7, 2022 at 0:27
  • 1
    Routers route packets between networks. Devices that do that are routers. Even layer-3 switches have a router built in. The process of forwarding packets between networks is called routing, and that is done by a router.
    – Ron Maupin
    Commented Apr 7, 2022 at 0:30
  • 1
    The difference you seem to make is "a router forwards within private LAN and a gateway routes to/from the rest of the world". That distinction doesn't exist - forwarding by IP address is routing and a router between networks is a gateway. The private/public addressing edge requires NAT for IPv4 but it does not for IPv6.
    – Zac67
    Commented Apr 7, 2022 at 4:50

1 Answer 1


A nat gateway is a term that Amazon made up. It’s not the same meaning used in traditional routing.

  • for the traditional routing, the scenario described in diagram doesn't exist. And if the router loses the gateway function, it can't be called router anymore. Am I understanding correctly?
    – Ryan Lyu
    Commented Apr 7, 2022 at 3:01
  • 2
    I think you're forcing a precise definition on a term that doesn't have one. There really isn't a "gateway function".
    – Ron Trunk
    Commented Apr 7, 2022 at 13:18

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