Port 389 (TCP/UDP) — LDAP

Check if port 389 is open

On the server, see what is listening:

sudo ss -tulpn | grep ':389 '

From another machine, test reachability:

nc -zv your-server.example.com 389

Block port 389 from the internet

With UFW (Ubuntu/Debian):

sudo ufw deny 389

With firewalld (RHEL/AlmaLinux/Rocky):

sudo firewall-cmd --permanent --remove-port=389/tcp && sudo firewall-cmd --reload

← All common ports