How do I find out my Linux gateway / router IP address?

Q. How do I find out my gateway IP for a computer or a network device that allows or controls access to another computer or network under Linux / UNIX?

A. A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes. In the network for an enterprise, a computer server acting as a gateway node is often also acting as a proxy server and a firewall server. A gateway is often associated with both a router, which knows where to direct a given packet of data that arrives at the gateway, and a switch, which furnishes the actual path in and out of the gateway for a given packet.

Find out Gateway / router IP address under Linux / UNIX

You need to use command called route. It manipulates the kernel’s IP routing tables. It can also use as follows to print gateway / router IP address:
$ route -n
Output:

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 ra0
0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 ra0

192.168.1.1 is gateway IP address for our computer. The flag U indicates that route is up and G indicates that it is gateway. You can print gateway name, enter:
$ route
Output:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     *               255.255.255.0   U     0      0        0 ra0
default         wrt             0.0.0.0         UG    0      0        0 ra0

Second column prints Gateway hostname / IP address. In our example wrt is gateway.

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