Port 389: LDAP
Directory lookups and authentication.
- Port
- 389
- Protocol
- TCP/UDP
- Service
- LDAP
- Exposure
- Do not expose to the internet
What is port 389 used for?
Active Directory and other directories.
Is it safe to expose port 389 to the internet?
Clear text by default. Use LDAPS on 636 or STARTTLS, and keep it internal.
If port 389 seems closed or unreachable
- Check that the LDAP service is running and listening on port 389, not only on 127.0.0.1.
- Check the firewall on the host itself (Windows Defender Firewall, iptables, nftables, ufw) for a rule that allows TCP 389.
- If the host is behind a router, confirm the forwarding rule points to the correct internal address and that your internet provider does not use carrier-grade NAT.
- Test from outside your own network. A port can be open locally and blocked at the edge, or the other way round.
Using port 389 safely
Treat port 389 as an internal-only service. Reach it through a VPN or an SSH tunnel, restrict it by source address, and keep the software that listens on it patched.
Check whether port 389 is open on your host
The check connects from our server, so it shows what the internet can reach.
Open the port checker