How to find the gateway IP address in Linux

Question

What command can you use to find the Gateway IP Address (ie. home router address) for eth0 in Linux?

I need to get the IP address from a command line app to use in a shell script.

Answer 1

To print out only the default gw IP:

route -n | grep 'UG[ \t]' | awk '{print $2}'

To print out route information on all interfaces:

route -n

or

route -rn

Answer 2

You can get the system's default gateway from the output of netstat -r or route

Answer 3

ip route show 0.0.0.0/0 dev eth0 | cut -d\  -f3

is my entry :)

Answer 4

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.199.0   0.0.0.0         255.255.255.240 U         0 0          0 virbr1
192.168.200.0   0.0.0.0         255.255.255.240 U         0 0          0 virbr2
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan0
192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
0.0.0.0         192.168.1.254   0.0.0.0         UG        0 0          0 wlan0

The 0.0.0.0 is your default gateway, pointing to 192.168.1.254 at my place.

Answer 5

The output from route -n or netstat -rn, and search for the destination 0.0.0.0.

Answer 6

I prefer the iproute package:

# get the default route
ip route list | awk ' /^default/ {print $3}'
# get the default route but limit on eth0 (output may be empty)
ip route list dev eth0 | awk ' /^default/ {print $3}'

Answer 7

Are you looking for the external IP address of the router?

In the past I've used a screen scraping script to get that sort of thing from the router setup pages. Most home routers have a browser based setup that is easy to access from the inside. It's hard to give a general solution but you can use curl or wget to fetch the page and then use grep & awk to get the IP address.

Answer 8

netstat -rn |awk '{if($1=="0.0.0.0") print $2}'

this will cleanly print the gateway IP. (what would linux scripting be without awk?)

Answer 9

anyone shorter than this? =)

ip r | awk '/^def/{print $3}'

Answer 10

[rajat@chida /]$ netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.1.0     *               255.255.255.0   U         0 0          0 eth0
192.168.122.0   *               255.255.255.0   U         0 0          0 virbr0
default         192.168.1.1     0.0.0.0         UG        0 0          0 eth0
[rajat@chida /]$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.122.0   0.0.0.0         255.255.255.0   U         0 0          0 virbr0
0.0.0.0         192.168.1.1     0.0.0.0         UG        0 0          0 eth0
[rajat@chida /]$