I need to retrieve the default gateway on a Mac machine. I know that in Linux route -n will give an output from which I can easily retrieve this information. However this is not working in Mac OSX(Snow Leopard).
I also tried netstat -nr | grep 'default', but I was hoping for a cleaner output like that produced by route -n in Linux/Unix. netstat -nr lists all the interfaces and the default gateway for them.
Any kind of suggestion or a hint in the right direction will be appreciated.
I would use something along these lines...
netstat -rn | grep "default" | awk '{print $2}'
For getting the list of ip addresses associated, you can use netstat command
netstat -rn
This gives a long list of ip addresses and it is not easy to find the required field. The sample result is as following:
Routing tables
Internet:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.195.1 UGSc 17 0 en2
127 127.0.0.1 UCS 0 0 lo0
127.0.0.1 127.0.0.1 UH 1 254107 lo0
169.254 link#7 UCS 0 0 en2
192.168.195 link#7 UCS 3 0 en2
192.168.195.1 0:27:22:67:35:ee UHLWIi 22 397 en2 1193
192.168.195.5 127.0.0.1 UHS 0 0 lo0
More result is truncated.......
The ip address of gateway is in the first line; one with default at its first column.
To display only the selected lines of result, we can use grep command along with netstat
netstat -rn | grep 'default'
This command filters and displays those lines of result having default. In this case, you can see result like following:
default 192.168.195.1 UGSc 14 0 en2
If you are interested in finding only the ip address of gateway and nothing else you can further filter the result using awk. The awk command matches pattern in the input result and displays the output. This can be useful when you are using your result directly in some program or batch job.
netstat -rn | grep 'default' | awk '{print $2}'
The awk command tells to match and print the second column of the result in the text. The final result thus looks like this:
192.168.195.1
In this case, netstat displays all result, grep only selects the line with 'default' in it, and awk further matches the pattern to display the second column in the text.
You can similarly use route -n get default command to get the required result. The full command is
route -n get default | grep 'gateway' | awk '{print $2}'
These commands work well in linux as well as unix systems and MAC OS.
The grep utility is not needed. Awk can do it all:
netstat -rn | awk '/default/ {print $2}'
192.168.128.1
Note that if you have something like Parallels (or a VPN, or both) running, you may see two or more default routing entries - it will be true if you use the 'grep' suggestion above, too.
netstat -rn | awk '/default/ {print $2}'
192.168.128.1
link#12
and
netstat -rn | awk '/default/ {print $2}'
utun1
192.168.128.1
link#12
To set a variable (_default) for further use (assuming only one entry for 'default') .....
_default=$( netstat -rn inet | awk '/default/ {print $2}' ) # I prefer $( ... ) over back-ticks
In the case of multiple default routes use:
netstat -rn | awk '/default/ {if ( index($6, "en") > 0 ){print $2} }'
192.168.128.1
These examples tested in Mavericks Terminal.app and are specific to OSX only. For example, other *nix versions frequently use 'eth' for ethernet/wireless connections, not 'en'. This is also only tested with ksh. Other shells may need a slightly different syntax.
Using System Preferences:
Step 1: Click the Apple icon (at the top left of the screen) and select System Preferences.
Step 2: Click Network.
Step 3: Select your network connection and then click Advanced.
Step 4: Select the TCP/IP tab and find your gateway IP address listed next to Router.
Source: Stackoverflow.com