How to monitor firewall in Linux?

[test_qweqwe]

Hallo~!.
Someone monitoring Linux firewall?
How did you realize it?

Because windows firewall is easy to monitor.

[HiroshiSatoh · Accepted solution]

By default the reject log is not recorded.
To set it entirely (regardless of the zone), enable it with the --set-log-denied option.

firewall-cmd - set-log-denied all

It is recorded in facility.level = kern.warning of syslog.
Please check "/var/log/messages".