Change to \etc\network\interfaces does not take effect
I recently needed to make a change to the interfaces on a debian build.
I edited the \etc\network\interfaces file and changed the ip address for the eth1 interface and commented out the eth1:0 sub interface as it is not required for the time being.
I then downed the interface, checked using ifconfig the interface was down and the brought it back up.
On checking using ifconfig the sub interface that I had commented out was up and running and responding to a ping.
I then restarted networking \etc\network restart and once restarted checked the eth1:0 interface and it was again active.
A friend advised that the interface must be down before making any changes to the interface file - I have tried to find any confirmation of this without success. Does anyone know if this is a fact ?
What is the correct sequence/process to make changes to the interfaces ?
Thank you to any assistance.