Introduction to the RHEL firewall – firewalld
RHEL comes with two low-level network traffic filtering mechanisms: nftables, for filtering IP-related traffic, and ebtables, for transparent filtering in bridges. These mechanisms are static and use a set of rules to accept or reject traffic, though they do provide a myriad of other capabilities. In RHEL, they are both handled and managed dynamically by firewalld. Unless there is a specific need to have a very low-level usage of these low-level filtering mechanisms, please use firewalld (or its main command, firewall-cmd) instead. In this section, we will take a look at the firewall defaults in RHEL.
firewalld is installed by default in the system, which we can check by using the rpm command, so there is no need to install it:
[root@rhel-instance ~]# rpm -qa | grep firewalld firewalld-filesystem-1.0.0-3.el9_b.noarch firewalld-1.0.0-3.el9_b.noarch
If we have an installation that doesn’t include firewalld for some...