Hello I have a question, and mostly times I can't explain to much what is it
But I'll try

ISP router ----------- > Linux Server whith 5 IP's from ISP with installed proxy on it - Mikrotik Server with pppoe concentrator

what is the best way to share internet from linux server to mikrotik server but with transparent proxy set on, Now i'm using the iptables with Masquarading, but I'm not sure is that a good idea, becasue masquerade is used when you have to less outside ip to machines that after the server - I have them as much as I need.

Thanks for any reply, even some google links advices.