Blocking port 389 would primarily impact which directory service protocol?

Blocking port 389 would primarily impact which directory service protocol?

• A. FTP
• B. SSH
• C. Telnet
• D. LDAP

Answer: (D)

Port 389 is the default network port for the Lightweight Directory Access Protocol (LDAP), which is used to access and modify directory services like user accounts and permissions. Blocking this port would prevent clients from communicating with the directory service to perform lookups, binds, or updates, effectively disrupting authentication and directory queries. LDAP is the protocol behind many directory services (such as Active Directory and OpenLDAP), whereas the other listed protocols use different ports (FTP on 21, SSH on 22, Telnet on 23). Note that LDAP can also use port 636 for LDAP over TLS, but the standard, unencrypted LDAP communication—and thus the primary impact of blocking port 389—remains LDAP.

Port 389 is the default network port for the Lightweight Directory Access Protocol (LDAP), which is used to access and modify directory services like user accounts and permissions. Blocking this port would prevent clients from communicating with the directory service to perform lookups, binds, or updates, effectively disrupting authentication and directory queries. LDAP is the protocol behind many directory services (such as Active Directory and OpenLDAP), whereas the other listed protocols use different ports (FTP on 21, SSH on 22, Telnet on 23). Note that LDAP can also use port 636 for LDAP over TLS, but the standard, unencrypted LDAP communication—and thus the primary impact of blocking port 389—remains LDAP.