Now I've joined a company , they have a DHCP server and I have to turn my static IP to DHCP . But you know , when I change it by "netconfig" , chose the DHCP and save it , my network is unreachable when I "ping" a address .

I type ifconfig then , it not show me the DHCP IP that I should get , on ly 127.0.0.1 .

How should I do now ? When I turn back to windows , I change static IP to DHCP it work fine .

im guessing when you ifconfig -a the card shows up and that you have the right module loaded...

make sure you have the dhcp client deamon running, ps aux | grep dhcpcd, if it isnt then, /sbin/dhcpcd, then restart networking.

if that doesnt work check /etc/rc.d/rc.inet1.conf it should look something like this...

# Config information for eth0:
IPADDR[0]=""
NETMASK[0]=""
USE_DHCP[0]="yes"
DHCP_HOSTNAME[0]=""

doesnt sound like you need to supply the dhcp server hostname as it works in windows, that also eliminates the possiblity of it being the mac address.