Blocking port 389 would primarily affect which directory service protocol?

Blocking port 389 would primarily affect which directory service protocol?

• A. FTP
• B. HTTP
• C. LDAP
• D. SSH

Answer: (C)

Port 389 is the default port for LDAP, the directory service protocol used by systems like Active Directory and OpenLDAP. Blocking this port stops LDAP clients from connecting to directory servers, which prevents essential directory operations such as binding (authentication) and searching or retrieving user and group attributes. In practical terms, authentication and directory lookups that rely on LDAP would fail, disrupting access control and user management across services that rely on the directory. Other common services use different ports (FTP typically on 21, HTTP on 80, SSH on 22), so blocking port 389 would not primarily affect those protocols. (Note: LDAP can also run over TLS on 636, but the standard LDAP traffic is on 389, which is why blocking this port targets LDAP.)

Port 389 is the default port for LDAP, the directory service protocol used by systems like Active Directory and OpenLDAP. Blocking this port stops LDAP clients from connecting to directory servers, which prevents essential directory operations such as binding (authentication) and searching or retrieving user and group attributes. In practical terms, authentication and directory lookups that rely on LDAP would fail, disrupting access control and user management across services that rely on the directory.

Other common services use different ports (FTP typically on 21, HTTP on 80, SSH on 22), so blocking port 389 would not primarily affect those protocols. (Note: LDAP can also run over TLS on 636, but the standard LDAP traffic is on 389, which is why blocking this port targets LDAP.)