error when adding FTP port on iptables rule

Leandro Garcia asked:

I am trying to add FTP port on my iptable configuration which I suspect the reason I cannot access my FTP via FileZilla.



#  Allow all loopback (lo0) traffic and drop all traffic to 127/8 that doesn't use lo0
-A INPUT -i lo -j ACCEPT

#  Accept all established inbound connections

#  Allow all outbound traffic - you can modify this to only allow certain traffic

#  Allow HTTP and HTTPS connections from anywhere (the normal ports for websites and SSL).
-A INPUT -p tcp --dport 80 -j ACCEPT
-A INPUT -p tcp --dport 443 -j ACCEPT

#  Allow SSH connections
#  The -dport number should be the same port number you set in sshd_config
-A INPUT -p tcp -m state --state NEW --dport 22 -j ACCEPT

# Just added for FTP
-A INPUT  -p tcp -m tcp --dport 21 -m conntrack --ctstate ESTABLISHED -j ACCEPT -m comment --comment "Allow ftp connections on port 21"
-A OUTPUT -p tcp -m --dport 21 -m conntrack --ctstate NEW,ESTABLISHED -j ACCEPT -m comment --comment "Allow ftp connections on port 21"

-A INPUT -p tcp -m tcp --dport 20 -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -m comment --comment "Allow ftp connections on port 20"
-A OUTPUT -p tcp --dport 20 -m conntrack --ctstate ESTABLISHED -j ACCEPT -m comment --comment "Allow ftp connections on port 20"

#  Allow ping
-A INPUT -p icmp -j ACCEPT

#  Log iptables denied calls
-A INPUT -m limit --limit 5/min -j LOG --log-prefix "iptables denied: " --log-level 7

#  Drop all other inbound - default deny unless explicitly allowed policy


The only thing I added there is the script below the comment # Just added for FTP

Now when I try to load it using, iptables-restore < /etc/iptables.firewall.rules an error like this occur:

iptables-restore v1.4.12: Couldn't load match `--dport':No such file or directory

Error occurred at line: 25

I am no expert in here, and this is my personal VPS box which I use for random practice stuffs.

What seems to be the reason?

My answer:

It’s a typo.

You have:

-m --dport

It should have been:

-m tcp --dport

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