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I have come across articles advising for the following:
iptables -A INPUT -p tcp 1000:2000 -j ACCEPT
And others stating that the above will not work and iptables only supports multiple port declarations with the --multiport option.
Is there a correct way to open many ports with iptables?
This is the correct way:
iptables -A INPUT -p tcp --match multiport --dports 1024:3000 -j ACCEPT
As an example. Source here.
-I is somewhat safer than -A.
-A INPUT -j REJECT --reject-with icmp-host-prohibited at the end of the INPUT and other tables. Using -A adds the rule at the end of the table, after the final rule so it won't ever be considered as netfilter works on a first match wins basis. Using -I inserts the rule at the beginning of the table ans as such it will always be considered.
-I isn't always safer if you don't know the ruleset.
May 13, 2014 at 19:24
What you've been told is right, although you've written it wrong (you've forgotten --dport).
iptables -A INPUT -p tcp --dport 1000:2000 will open up inbound traffic to TCP ports 1000 to 2000 inclusive.
-m multiport --dports is only needed if the range you want to open is not continuous, eg -m multiport --dports 80,443, which will open up HTTP and HTTPS only - not the ones in between.
Note that the ordering of rules is important, and (as Iain alludes to in his comment elsewhere) it's your job to make sure that any rule you add is in a place where it will be effective.
TL;DR but...
Pure port range without multiport module:
iptables -A INPUT -p tcp --dport 1000:2000 -j ACCEPT
Equivalent multiport example:
iptables -A INPUT -p tcp -m multiport --dports 1000:2000 -j ACCEPT
...and variation about multi port with multi ranges (yes, this is also possible):
iptables -A INPUT -p tcp -m multiport --dports 1000,1001,1002:1500,1501:2000 -j ACCEPT
...and equivalent multi port multi range example with negation:
iptables -A INPUT -p tcp -m multiport ! --dports 0:999,2001:65535 -j ACCEPT
Have phun.
According to man iptables-extensions you can define a port range just by using the --dport switch.
tcp
These extensions can be used if `--protocol tcp' is specified. It provides the following options:
[!] --destination-port,--dport port[:port]
Destination port or port range specification. The flag --dport is a convenient alias for this option.
So this is also specifying a port range:
iptables -A INPUT -p tcp --dport 1000:2000 -j ACCEPT
there is an other way to add the entry directly on the Iptables file.
location /etc/sysconfig/iptables
-A INPUT -p tcp -m multiport --dports 1024:3000 -m state --state NEW -j ACCEPT
after that restart iptable service
NEW state, only the first packets are accepted. You can use NEW,ESTABLISHED,RELATED to allow incoming requests for the port range
Dec 12, 2021 at 18:40