save

open or create iptables script

# vim /etc/network/if-post-down.d/iptables

write these lines

#!/bin/bash
iptables-save > /etc/iptables.rules

save and make it executeable

# chmod +x /etc/network/if-post-down.d/iptables

restore

open or create file

# vim /etc/network/if-pre-up.d/iptables

save these lines

#!/bin/bash
iptables-restore < /etc/iptables.rules

make it executable as well

# chmod +x /etc/network/if-pre-up.d/iptables