Enabling and managing services and ports

As we mentioned in the previous section, a firewalld service is a port or group of ports that are configured together for a specific system service (hence the name) to work properly. There are a set of services that are enabled by default in one or many of the available firewalld zones. Let’s start by reviewing them:

• ssh: Provides access to the Secure Shell (SSH) service in the system, which also enables remote management. The traffic that’s accepted goes to port 22 and is of the TCP type.
• mdns: Provides access to the Multicast DNS (MDNS) service that’s used to announce services in the local network. Traffic is accepted to multicast address 224.0.0.251 (IPv4) or ff02::fb (IPv6), on port 5353, and is of the UDP type.
• ipp-client: Provides access to the Internet Printing Protocol (IPP) client, which goes to port 631 and uses the UDP protocol.
• samba-client: This is a file and print sharing client that’...