iptables and OUTPUT chain
I have been learning about iptables and I am looking at the default tables and the default chains within them. I would like to know why both the FILTER and NAT tables have an OUTPUT chain. According to my research, rules added to the OUTPUT chain will affect outgoing packets that were generated by the local machine. This seems to be the case for the OUTPUT chain in both tables. So why have them in both? Is it simply a difference in the order in which the chains are executed? Is there some advantage of altering the OUTPUT chain in one table as opposed to the other?