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Difficulty: HardNetworking Ports and Protocols

A systems engineer is configuring an identity management server that communicates with Active Directory for central authentication. Organization security policy mandates that all directory lookup queries containing credential verification must be encrypted in transit using SSL/TLS. During testing, standard unencrypted queries are blocked by default as expected, but encrypted authentication attempts also fail. Firewall log analysis confirms that outbound traffic from the identity server to the directory server on the secure directory service port is being dropped. Which of the following port and transport protocol combinations must be permitted on the firewall to resolve the issue?

  1. A
    TCP 389
  2. B
    UDP 67
  3. TCP 636Answer
  4. D
    TCP 445

Answer

TCP 636 must be allowed through the firewall because it is the standard port designated for LDAPS (Lightweight Directory Access Protocol over SSL/TLS), satisfying the mandate for encrypted directory queries.
The correct answer specifies TCP port 636, which is the standardized default port for LDAPS (Lightweight Directory Access Protocol over SSL/TLS). LDAPS wraps directory access queries inside an encrypted session layer, fulfilling the organizational requirement for secure authentication.

Step-by-Step Solution

1
Identify the required service and security posture from the scenario.
The scenario requires directory service communication (LDAP) with mandatory SSL/TLS encryption.
Security policy dictates that credential verification queries must not travel unencrypted.
2
Differentiate between unencrypted and encrypted default ports for directory services.
Standard unencrypted LDAP operates on TCP port 389, whereas LDAPS operates on TCP port 636.
Knowing the specific port number for the secure variant is essential for writing accurate firewall rules.
3
Select the correct port and transport protocol matching LDAPS.
TCP port 636 is the correct specification.
Allowing TCP 636 permits encrypted Active Directory communication through the security appliance.

Key Concept

LDAP vs. LDAPS Secure Directory Ports
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Topics

Networking Ports and Protocols

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