Why does '~$ sudo ifup eth0' not provide Internet access?

[Detlef Lechner]

Hi, 
[LAN using pm-utils and Fritz!BoxFon ADSL router] I'm resuming my Hardy 
computer from hibernation. I notice that I forgot to switch on prior
the 
router. 
'~$ sudo ethtool eth0' reports 'Link detected'. 
sudo ifdown eth0 reports: "interface eth0 not configured." 
'~$ sudo ifup eth0' still does not provide Internet access. Only 
'sudo /etc/dbus-1/event.d/25NetworkManager restart' provides Internet 
access. 
Why?

Regards,
Detlef Lechner