Error when doing port forwarding with iptables?

Question

I've got a fairly standard ubuntu install and looking to add a port forward.

*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT

#Redirect 1731 to  8443
-t nat -A PREROUTING -i eth0 -p tcp --dport 1731 -j REDIRECT --to-port 8443

#Allow 443 and 80
-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT


-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT

However I keep getting an error:

iptables: Applying firewall rules: iptables-restore v1.4.7: Line 13 seems to have a -t table option.

I've confirmed that ip forwarding is enabled on that device:

cat /proc/sys/net/ipv4/ip_forward 
1

I'm sure it's something simple in the formatting of iptables that I am missing. Thoughts?

Answer 1

The line which starts with -t nat shouldn't be under the filter table, as denoted by the first line.

Change the file to the following:

*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT

#Allow 443 and 80
-A INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT

-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A FORWARD -j REJECT --reject-with icmp-host-prohibited

COMMIT

*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:POSTROUTING ACCEPT [0:0]

#Redirect 1731 to  8443
-A PREROUTING -i eth0 -p tcp --dport 1731 -j REDIRECT --to-port 8443

COMMIT