12

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.

3
  • 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. – Tom Bascom Jun 24 '09 at 18:29
  • I should have been clearer in my question. Basically, I want to find the gateway IP address that is set to eth0 on a box that has a single ethernet interface. Coincidentally, this should be the IP address of a home, basic, Linksys-type or so, NAT router. I need it so I can ping it in a shell script. – J. Polfer Jun 24 '09 at 18:43
  • Seems more complex than what I need, but a cool, guaranteed-to-work idea though. – J. Polfer Jun 24 '09 at 18:44

11 Answers 11

21

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

netstat -rn
5
  • Wouldn't UG require the interface to be up? I think just G would be better. – J. Polfer Jun 24 '09 at 18:39
  • Either way, this is spot on. Many Thanx. – J. Polfer Jun 24 '09 at 18:40
  • Wanted to let you know - I'm actually using this answer, but with just a G in the grep pattern; didn't have iptools on the machine i need to run this on. – J. Polfer Jun 24 '09 at 21:09
  • 2
    You can save yourself the grep, awk can also filter: route -n | awk '{if($4=="UG")print $2}' – Kenny Rasschaert Dec 20 '11 at 7:16
  • I would suggest something like route -n|awk '$4~/G/{print $2; exit(0)}' for the first gateway, but ip route get IP is better, because it lists the route which would be really taken to the given IP, which is difficult to find with route alone – Tino May 24 '13 at 13:32
12
ip route show 0.0.0.0/0 dev eth0 | cut -d\  -f3

is my entry :)

5
  • I would improve this one: ip route show 0.0.0.0/0 | awk '{print $3}' – Dominic Eidson Jun 24 '09 at 19:38
  • I dunno... mine's still fewer keystrokes :) – MikeyB Jun 24 '09 at 20:57
  • 1
    And cut is ~20 times lighter binary than awk. – K3---rnc Oct 4 '15 at 12:06
  • If I leave off the "dev eth0" does it work for either eth0 or wlan0 ? (I would try this if I had a long enough lan cable) – Eric Nelson May 16 '18 at 19:39
  • Its worked for me for openwrt os :) – Joy Acharya May 19 '20 at 14:22
5

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

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$ 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.

2

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

2

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}'
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  • @sheepsimulator: Unfortunately, this is a bad assumption to make. Supermathie's suggestion is better. – Dominic Eidson Jun 24 '09 at 19:34
  • @Dominic Eidson - Why? There's only one physical ethernet interface on the machine. – J. Polfer Jun 24 '09 at 19:40
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    exactly what is a bad assumption? – Martin M. Jun 24 '09 at 23:03
2

anyone shorter than this? =)

ip r | awk '/^def/{print $3}'
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  • 1
    Challenge accepted: ip r | awk 'END{print $3}' is three characters shorter. – Kenny Rasschaert Dec 20 '11 at 7:13
  • nice, but on my local debian/squeeze box with KVM bridges my default gw is in line one. strange but true. So your cool solution doesn`t work everywhere :-/ (anyhow +1 ) – ThorstenS Dec 20 '11 at 7:27
  • ip is not a generic UNIX command - so again it won't work everywhere. – Mei Dec 20 '11 at 15:55
  • you are right, but in $Subject stands Linux and not UNIX ;) @David: wow, you have really nice blog! – ThorstenS Dec 20 '11 at 17:06
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    read x x i x< <(ip r g 1), result is in variable $i for further use – Tino May 24 '13 at 13:18
1

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?)

1
  • Then you'd have to use sed instead... netstat -rn|sed -n '/^0.0.0.0/{ s/^[0. ]*//; s/ .*$//; p; } – Mei Dec 20 '11 at 15:53
0

If you would like to get the gateway from the interfaces file:

#!/bin/bash
gateway=$(grep -P '^\tgateway' /etc/network/interfaces)
gateway=$(echo ${gateway:9})    # Remove "  gateway "   
echo "gateway = $gateway"
if [ $gateway == "" ]; then
    echo "gateway is blank"
    exit -1
fi
0

My one liner command to get the default gateway IP address :

route | grep default | awk '{print $2}'
-2

Open Terminal on your Linux OS It’s usually located in the top bar or bottom bar, depending on the Linux distribution you use Once you have opened the Terminal window, enter the following commands “ip route | grep default” Now wait a second for the output and note your default gateway address on the screen Your gateway address should look something like 192.168.1.1. Once you know it, you can start configuring your router via its web admin panel.

If this didn't fix your network, you may need a new router.

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