Ptp4l resp. multicast not working on 9.1


I installed linuxptp via
sudo yum install linuxptp

I read everything regarding reverse path filtering and configured correctly:
cat /proc/sys/net/ipv4/conf/default/rp_filter reports 0
cat /proc/sys/net/ipv4/conf/all/rp_filter reports 0
cat /proc/sys/net/ipv4/conf/ens1/rp_filter reports 0
ens1 is Intel I210.

But there’s no IPv4 multicast traffic arriving (can be sent though). Reading timestamps via the error queue does work though, but no multicast PTP messages can be read.

Could anybody be so kind and explain how one can make ptp4l work on AlmaLinux 9.1?

Thank you.

It’s firewalld that with its default settings doesn’t even let pass well known multicasts.

There is already a ptp rule configured in the firewalld configuration, but it’s needed to activate it for the firewall zone of the used network interface.