Permament iptables port forwarding?
Which GNU/Linux distribution are you using?
For Debian/Ubuntu the simple solution is to add the iptables call to a post-up hook in /etc/network/interfaces like this:
# The primary network interface
auto eth0
iface eth0 inet dhcp
post-up iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 7000
On Red Hat/Fedora based systems:
service iptables save
And make sure that the iptables service is set to start on boot: chkconfig iptables on