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 BascomJun 24, 2009 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. PolferJun 24, 2009 at 18:43
-
Seems more complex than what I need, but a cool, guaranteed-to-work idea though.– J. PolferJun 24, 2009 at 18:44
Add a comment
|
12 Answers
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
-
Wouldn't UG require the interface to be up? I think just G would be better. Jun 24, 2009 at 18:39
-
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. Jun 24, 2009 at 21:09
-
2You can save yourself the grep, awk can also filter:
route -n | awk '{if($4=="UG")print $2}'Dec 20, 2011 at 7:16 -
I would suggest something like
route -n|awk '$4~/G/{print $2; exit(0)}'for the first gateway, butip route get IPis better, because it lists the route which would be really taken to the given IP, which is difficult to find withroutealone– TinoMay 24, 2013 at 13:32 -
ip route show 0.0.0.0/0 dev eth0 | cut -d\ -f3
is my entry :)
-
I would improve this one: ip route show 0.0.0.0/0 | awk '{print $3}' Jun 24, 2009 at 19:38
-
-
1
-
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) May 16, 2018 at 19:39
-
You can get the system's default gateway from the output of netstat -r or route
answered Jun 24, 2009 at 18:25
$ 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.
Since iproute2 4.14.1, you can also output JSON for a lot of commands.
So this would work:
ip -j route show 0.0.0.0/0 dev <interface> | jq -r '.[0].gateway'
In your case:
ip -j route show 0.0.0.0/0 dev eth0 | jq -r '.[0].gateway'
Note that you need jq for this, but depending on your environment that might already be available - I know it was in my case.
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}'
answered Jun 24, 2009 at 18:40
-
@sheepsimulator: Unfortunately, this is a bad assumption to make. Supermathie's suggestion is better. Jun 24, 2009 at 19:34
-
@Dominic Eidson - Why? There's only one physical ethernet interface on the machine. Jun 24, 2009 at 19:40
-
2
The output from route -n or netstat -rn, and search for the destination 0.0.0.0.
anyone shorter than this? =)
ip r | awk '/^def/{print $3}'
-
2Challenge accepted:
ip r | awk 'END{print $3}'is three characters shorter. Dec 20, 2011 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 ) Dec 20, 2011 at 7:27
-
-
you are right, but in $Subject stands Linux and not UNIX ;) @David: wow, you have really nice blog! Dec 20, 2011 at 17:06
-
2
If you would like to get the gateway from the interfaces file:
#!/bin/bash
gateway=$(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
netstat -rn |awk '{if($1=="0.0.0.0") print $2}'
this will cleanly print the gateway IP. (what would linux scripting be without awk?)
-
Then you'd have to use sed instead...
netstat -rn|sed -n '/^0.0.0.0/{ s/^[0. ]*//; s/ .*$//; p; }– MeiDec 20, 2011 at 15:53
My one liner command to get the default gateway IP address :
route | grep default | awk '{print $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.
