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