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Port 636 (LDAPS) — What It Is and How to Use It

Port 636 is the standard port for LDAPS (Lightweight Directory Access Protocol Secure), which is a secure version of LDAP. It encrypts LDAP communication using SSL/TLS, protecting sensitive directory information during transmission. This is crucial for maintaining the confidentiality and integrity of user credentials and other directory data.

Last updated: 2026-06-11

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Port Number 636
Protocol LDAPS

Common Use Cases

  • Secure authentication against Active Directory or other LDAP-compliant directories.
  • Centralized user management and authorization in enterprise environments.
  • Secure access to directory services for applications and network devices.
  • Synchronizing user data between different systems securely.

Interactive Command Builder

nc -zv example.com 636

Check if Port 636 is Open

Linux: `nmap -p 636 <target_ip>` or `ss -tlnp | grep 636`
Windows: `netstat -ano | findstr :636` or `Test-NetConnection -ComputerName <target_ip> -Port 636` (PowerShell)
⚠️ Security Note: Leaving port 636 open without proper configuration and strong SSL/TLS certificates can expose directory services to various attacks. It's essential to use strong encryption protocols, regularly update certificates, and restrict access to trusted IP addresses.

Related Ports

Port 389 Port 3268 Port 3269

Frequently Asked Questions

Is port 636 dangerous to leave open?

Yes, if not properly secured. While LDAPS itself is designed for security, an improperly configured server or weak SSL/TLS certificates can make it vulnerable to eavesdropping, man-in-the-middle attacks, or unauthorized access to directory data. It should only be accessible to trusted clients and secured with strong encryption.

What service uses port 636?

Port 636 is used by LDAPS (Lightweight Directory Access Protocol Secure). This is the secure version of LDAP, which is a protocol for accessing and maintaining distributed directory information services.