You can get dhclient to do custom things as it creates your config. (I'm assuming Fedora uses dhclient and not one of the other DHCP clients.)
Edit /etc/dhclient.conf and change (or add) a line that starts with "prepend domain-name-servers". The rest of the line should list the ISP's DNS servers, that you want to make permanent.
My /etc/dhclient.conf looks like this:
Code:
prepend domain-name-servers 127.0.0.3;
and that's all.