Two questions about networking

1. If I have a network setup where the internet comes through the modem, then into the router, and then to the computers, the default "gateway" for the router should be the modem, correct?

2. What is the difference, in a router, between "gateway" mode and "router" mode? Is gateway mode used for passing on the internet connection to computers connected to it? So that the gateway for the computers is the router, and the gateway for the router is the modem and the modem connects to the isp or internet or whatever?

 

1. No, the modem serves as a bridge between the ethernet network in your LAN and the broadband network from your ISP. The default gateway exists at your ISP although some modem give IP addresses to routers when they can't get one from the ISP.

2. A gateway (in the context of what we're discussing) is a device that forwards packets to another network. When your router is in gateway mode it basically connects to your ISP's network and shares that connection with all the device connected to it. Router mode is used when you are connecting routers together.

 

The default gateway would be the router. That is the place you network will send traffic that is not for the local network. See when you add a router you are creating a network. So there is the network behind the router and the network between the router and "modem".. that is where NAT comes in - that is another lesson.
This is way bigger than that answer, so for simplistics the router is the gateway.

 

If you are talking about a setting in the Router.

When using more than one computer on a single connection you have to use the Router as a Router.