How to execute a script only once, immediately after ALL network interfaces are up in OpenSUSE?

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http://serverfault.com – I run Opensuse 12.2. I have 3 network interfaces, eth[012] The interfaces are configured in /etc/sysconfig/network/ifcfg-eth[012] I want to execute a script immediately after ALL three interfaces are 'up'. Adding POST_UP_SCRIPT="/path/to/script.sh" to ifcfg-eth[012] executes the script after any ONE interface is up. Placing the script in /etc/sysconfig/network/if-up.d/script.sh executes the script multiple times - once after EACH interface is up. How do I execute the script ONLY ONCE, immediately after the last interface is brought up? (HowTos)