[ILUG] Ubuntu networking questions

[Niall O Broin]

On a breezy box,  man interfaces says (abbreviated)

pre-up command
               Run command before bringing the interface up.
up command

post-up command
               Run command after bringing the interface up.

down command

pre-down command

post-down command
               Run command after taking the interface down.

I'm curious as to when exactly the up and down commands are run. Surely 
they must be synonymous with either pre-up/post-up   and  
pre-down/post-down ?


And on that note, is there a kosher way of adding a secondary IP 
address to an interface via the interfaces file, or is something like

post-up ip addr add a.b.c.d/n dev ethX

the only way to do it?