Load balancing LDAP Servers

Updated on April 2, 2025
Published on March 7, 2023

About LDAP (Lightweight Directory Access Protocol)

LDAP (Lightweight Directory Access Protocol) is an open, cross-platform application protocol. It is designed to allow information to be shared regarding hosts, users, DNS, certificates, printers, and more in a network. A commonly used implementation is OpenLDAP, as well as Microsoft Active Directory which features LDAP support. LDAP can also be used with Kerberos to provide authentication services.

Key benefits of load balancing

Here are a few key benefits:

  • Ensures the application is always available
  • Provides a stable, optimal performance
  • Uninterrupted uptime when performing upgrades/maintenance

How to load balance LDAP Servers

Loadbalancer.org appliances can be used in conjunction with a cluster of LDAP servers to provide a highly available LDAP service. Using load balancers also makes LDAP server maintenance easier, as well as making the service scalable should additional servers needed to be added in the future to increase capacity.

Protocol Role Default Ports Supported Load Balancing Methods
TCP/UCP/LDAP For LDAP communication 389 (or 3268 for Global Catalog access on a Microsoft AD server) Layer 4 DR, Layer 4 NAT, Layer 7 TCP
TCP/UDP/LDAPS (“LDAP over SSL”) For LDAP communication using TLS/SSL 636 (or 3269 for Global Catalog access over TLS/SSL on a Microsoft AD server) Layer 4 DR, Layer 4 NAT, Layer 7 TCP