Home / server / Questions / 269784
Accepted
koddo
Asked: 2011-05-15 12:31:31 +0800 CST

iptables masquerading and rejecting outside-to-inside

  • 772

I found masquerading made simple howto very useful and everything works just fine. But I'm not sure about the last line:

iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m state --state NEW -i ! ppp0 -j ACCEPT
iptables -P INPUT DROP   #only if the first two are succesful
iptables -A FORWARD -i ppp0 -o ppp0 -j REJECT

There is no explanation in the howto. Why is that for?

I guess it's to reject outside-to-inside traffic, but how it works? Maybe it's better to write -i ppp0 -o eth0 (where eth0 is my local network interface)?

nat iptables

1 Answers

  1. Best Answer

    The FORWARD table is used to manage packets that are being routed though the box. That rule basically stops anything being routed via the ppp0 interface.

    • 4