Opening, blocking and changing ports on RedHat

[Eric Shubert]

On 01/04/2011 12:52 PM, keith smith wrote:
>
> Hi,
>
> I'm working on several CentOS and one RHEL servers. I needed to open a
> port the other day so I did a search and the info I found lead me to
> believe the only way to open or close a port was via iptables. Is that
> the complete story?
>
> For example, if I want to open port 3306 for MySql I need two things? 1)
> The port needs to be listed in /etc/services (RedHat) and 2) the port
> needs to be opened via iptables.
>
> If I use a non-standard port (3306) I must add a line to the
> /etc/my.conf that defines the port such as "port=xxxx".
>
> Here is a twist. I set my SSHD to port 2200 but did not change
> /etc/services, which lists ici on port 2200 for both tcp and udp. I am
> able to shell in using port 2200. Why no conflict?
>
> Thank you for your insight.
>
> ------------------------
> Keith Smith

I don't know if /etc/services is actually used by anything aside from 
name->port resolution (service name to port number). As long as the 
configuration for the service in question is specified using a port 
number (as opposed to a service name), I don't think the /etc/services 
file would come into play. (how/why would it?)

-- 
-Eric 'shubes'