mmmmhhhh.... I found the error... my error !!!! :-/I did "ifconfig add eth0:2 my_ip " in place of "ifconfig eth0:2 my_ip up" ; it's why Debian added a "eth0:2:0" .
"add" and "up" have a different behavior...!!! stupid guy !!!
thanks for your help :-) Benoit Lathiere.
