What does the following iptables rule accomplish:
iptables A INPUT d 10.142.232.1 p tcp dport 20:21 j ACCEPT
A.
Forwards all traffict on port 20 or 21 to the host 10.142.232.1.
B.
Drops all traffic coming from the host 10.142.232.1 destined for port 20 or 21.
C.
Accepts all traffic from the host 10.142.232.1 destined for port 20 or 21.
D.
Forwards all traffic on port 20 and 21 to the host 10.142.232.1.