The FTP protocol doesn't use UDP at all, so it isn't any surprise that cPanel's documentation doesn't suggest that you open port 20 and 21 UDP on the firewall.
How to Configure Your Firewall for cPanel Services - cPanel Knowledge Base - cPanel Documentation
However...
I've been looking at our software firewall configs and I noticed that the CSF default has UDP ports 20 and 21 open.
I wonder if there is something specific to Pure-FTP that requires these ports to be open? When looking around for info about this, I have seen several websites that suggest UDP ports 20 and 21 should be enabled for both inbound and outbound on a cpanel server.
Can anyone confirm that this is actually necessary?
How to Configure Your Firewall for cPanel Services - cPanel Knowledge Base - cPanel Documentation
However...
I've been looking at our software firewall configs and I noticed that the CSF default has UDP ports 20 and 21 open.
I wonder if there is something specific to Pure-FTP that requires these ports to be open? When looking around for info about this, I have seen several websites that suggest UDP ports 20 and 21 should be enabled for both inbound and outbound on a cpanel server.
Can anyone confirm that this is actually necessary?