OSX:RunWhenNetworkChanges

How To run a script when the networking location changes

Create the script you want to run.

$ vim /Users/mdsh/bin/route-add

#!/bin/bash

route delete 10.0.0.0/8 10.64.0.253
route add 10.0.0.0/8 10.64.0.253

Make the script runnable.

$ chmod a+x /Users/mdsh/bin/route-add

Create a plist which defines a script to be run upon the detection of a change in a networking file.

$ sudo vim /Library/Preferences/SystemConfiguration/com.mdsh.createRoutes.plist

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" \
 "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>Label</key>
  <string>ifup.ddns</string>

  <key>LowPriorityIO</key>
  <true/>

  <key>ProgramArguments</key>
  <array>
	 <string>/Users/mdsh/bin/route-add-leyborne</string>
  </array>

  <key>WatchPaths</key>
  <array>
	 <string>/etc/resolv.conf</string>
	 <string>/Library/Preferences/SystemConfiguration/NetworkInterfaces.plist</string>
	 <string>/Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist</string>
  </array>

  <key>RunAtLoad</key>
  <true/>
</dict>
</plist>

Load the plist.

$ sudo launchctl load /Library/Preferences/SystemConfiguration/com.mdsh.createRoutes.plist

OSX:RunWhenNetworkChanges is mentioned on: OSX