Time and again, whenever I look at the Firewalld rules, I find myself wondering here and there what the services actually do, what effect they have, what kind of Internet traffic they allow through, and so on. I’ve searched various Firewalld pages, but I just can’t find a description of the abbreviations—which aren’t always self-explanatory—explaining what they mean and what they do. I did find a list on Red Hat, but it didn’t include any explanations of the individual services. list of services supported by firewalld
Afterwards the setting of my home-zone
<zone>
<short>Home</short>
<description>
For use in home areas. You mostly trust the other computers on networks to not harm your computer. Only selected incoming connections are accepted.
</description>
<service name="ssh"/>
<service name="mdns"/>
<service name="samba-client"/>
<service name="dhcpv6-client"/>
<service name="slp"/>
<forward/>
</zone>
Where the Service “Samba-client” is relatively self-explanatory, services like “slp” aren’t.
Well, I can get some tech. infos by the firewall-cmd command.
There’s a list of services and the commonly used ports here:
The ports below 1024 are probably the most noteworthy.
It’s worth noting too, that port numbers can be changed, or used by multiple pieces of software. So for example, if you notice port 777 has been opened on your system, it could quite literally be anything and doesn’t have to match what’s in that list. The same goes for most all port numbers.
From what you’ve shared, it’s not clear why slp / 427 might be open on your firewall. You could continue to monitor, or you could simply disable that port and see what stops working
As slp TCP port 27 seems necessary for HP-Printers as I found out as a quick research. I think I will delete it as I don’t have such a printer anymore.
