Glossary · Networking

LDAP (Lightweight Directory Access Protocol)

LDAP is a protocol for querying and updating hierarchical directories of users, groups and devices, widely used for centralized authentication.

Updated October 6, 2026

LDAP (Lightweight Directory Access Protocol) is a protocol for reading and modifying entries in a directory service, a hierarchical database optimized for lookups of people, groups, computers and other objects. It listens on TCP port 389, or 636 for LDAPS (TLS).

Why it matters

Organizations keep accounts in a central directory such as Microsoft Active Directory or OpenLDAP, and applications, VPNs, Wi-Fi systems and mail servers ask it who a user is and which groups they belong to. One place to disable an account then cuts access everywhere. LDAP often sits behind RADIUS or SSO systems.

Entries are named by a distinguished name (DN) that describes their position in the tree.

Example

ldapsearch -H ldaps://ldap.example.com \
  -b "dc=example,dc=com" "(uid=asha)" cn mail

This searches under dc=example,dc=com for the user asha and returns the cn and mail attributes. A typical DN is uid=asha,ou=People,dc=example,dc=com.

Common mistakes

  • Sending bind passwords over plain LDAP on port 389 without StartTLS.
  • Building filters from unescaped user input, which allows LDAP injection.
  • Confusing LDAP with Active Directory; LDAP is the protocol, AD is one product that supports it.

Get notified when this term updates

Plus occasional practical tips on uptime and monitoring, nothing else. Unsubscribe anytime.

Keep reading

Glossary · Networking802.1X (Port-Based Network Access Control)802.1X is an IEEE standard that blocks a network port until the connecting device authenticates, commonly with a RADIUS server.Glossary · NetworkingAccess Point (Wireless AP)A wireless access point is a device that connects Wi-Fi clients to a wired network, acting as the bridge between radio and Ethernet.Glossary · NetworkingAnycast RoutingAnycast announces the same IP address from many locations, so network routing sends each user to a nearby site and absorbs traffic floods.

This page is general information written by our editorial team and updated when documentation changes. Servers and providers differ, so test changes safely first. See our editorial policy and disclaimer.