How to disable packets via iptables?

Question

System administration

There is a gateway to ubuntu-server, it is also a firewall. It is necessary to prohibit a certain IP from sending and receiving any packets through the external interface. I tried to do like this:

$ip -A FORWARD -s 10.40.1.250 -i $EXTERNAL -j DROP
$ip -A FORWARD -o $EXTERNAL -d 10.40.1.250 -j DROP

So:

iptables -I OUTPUT -s 10.40.1.250 -m conntrack --ctstate NEW, ESTABLISHED -j DROP

But it does not help, there is still access to the Internet. Any ideas how to block packet transmission and reception from the external interface? Thank you

Answer 1

iptables -I FORWARD -s 10.40.1.250 -i $LAN_ETH -j DROP