Обход администратора сети

Администратор сети игнорирует NICs, упомянутый в /etc/network/interfaces по умолчанию. Ничего не добавляйте о другом NICs в том файле. От man NetworkManager.conf :

[ifupdown]
   This section contains ifupdown-specific options and thus only has effect 
   when using ifupdown plugin.

   managed=false | true
          Controls  whether  interfaces  listed in the 'interfaces' file are 
          managed by NetworkManager.  If set to true, then interfaces listed in 
          /etc/network/interfaces are managed by NetworkManager.  If set to 
          false, then any interface listed in /etc/network/interfaces will be 
          ignored by NetworkManager. Remember that NetworkManager controls the 
          default route, so because the interface is ignored, NetworkManager may 
          assign the  default  route to some other interface. When the option is 
          missing, false value is taken as default.