[CentOS] command for dhcp client

Is there a command that says DONT use the ifcfg-eth0 setting(s)
that basically have a static address and start the network in DHCP.

I dont want to disturb the static settings in ifcfg-eth0 or re-enter them
once my DHCP setting is done...

I just want to temporarily run with DHCP (I'm on different network than 
the static setup).

Yes I can copy files and then recopy files and all that - but is there a 
command that
just says startup the network in DHCP and dont change anything in the 
files.

Jerry