iptables --dport ssh

Question

In iptables, what is the difference between --dport ssh and --dport 22? i.e. when I change the port in sshd's settings, will iptables automatically get the new port and use that wherever --dport ssh is specified, or will it still use 22?

Answer 1

When you use a name it will do a look-up on what is defined in your /etc/services. What you have defined in your openssh's sshd_config is completely irrelevant. The name is only evaluated when the rule is being added to the kernel tables. Once the rule has been added, any subsequent changes to /etc/services do not automatically result in a change of the rule.