Iptables FORWARD chain: br0 or ppp0

[user2k10]

I have an RT-AC68U and it is connected to my fibre modem via the wan port using a PPPoE connection.

I want to add some rules to the FORWARD chain to block outgoing and incoming packets from the Internet.

iptables -I FORWARD -i br0 -o ppp0 -m set --match-set Microsoft dst -j DROP
iptables -I FORWARD -o br0 -i ppp0 -m set --match-set Microsoft src -j DROP

I am confused about when to use br0 and when to use ppp0.

To block outgoing packets to the internet do I specify -i br0 -o ppp0 or do I only specify -o ppp0?

To block incoming packets from the internet do I specify -i ppp0 -o br0 or do I only specify -i ppp0?

Please explain if you can.

Thanks

 

[RMerlin]

FORWARD implies traffic comes from one interface, and goes to another interface. br0 is your local LAN, and ppp0 is your Internet interface. So if you want to stop something that comes from the Internet and goes into your LAN, it would be -i ppp0 -o br0.