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J. Polfer
Asked: 2009-06-25 10:22:29 +0800 CST

How to find the gateway IP address in Linux

  • 772

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.

linux scripting shell tcpip gateway

12 Answers

  1. Best Answer

    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
    • 29 
  2. ip route show 0.0.0.0/0 dev eth0 | cut -d\  -f3

    is my entry :)

    • 15

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

    • 5 
  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.

    • 3

  5. 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}'
    • 3

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

    • 2

  7. anyone shorter than this? =)

    ip r | awk '/^def/{print $3}'
    • 2

  8. 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.

    • 2

  9. 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?)

    • 0

  10. 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