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Question

Difficulty: HardCommon Ports and Protocols

A network administrator is establishing stateless inbound Access Control List (ACL) rules on an internal gateway router to allow remote network infrastructure monitoring and log aggregation. The management policy mandates that managed switches send encrypted log events via Secure Syslog (Syslog-TLS) to a central server while concurrently synchronizing system clocks with a dedicated internal time server. Which combination of transport layer protocols and destination port numbers must be permitted on the router to support both Secure Syslog and Network Time Protocol (NTP) traffic?

  1. TCP port 6514 for Secure Syslog and UDP port 123 for NTPAnswer
  2. B
    UDP port 514 for Secure Syslog and TCP port 123 for NTP
  3. C
    TCP port 514 for Secure Syslog and UDP port 512 for NTP
  4. D
    IP protocol 514 for Secure Syslog and IP protocol 123 for NTP at Layer 3

Answer

The correct rule configuration permits TCP port 6514 for Secure Syslog and UDP port 123 for NTP.
Secure Syslog (RFC 5425) specifies TCP port 6514 for transport layer security (TLS) log transmission to ensure confidentiality and reliable delivery. Network Time Protocol (NTP) utilizes UDP port 123 to handle low-latency timestamp exchanges across network devices.

Step-by-Step Solution

1
Identify the transport protocol and port number required for Secure Syslog (Syslog-TLS).
Standard unencrypted Syslog uses UDP port 514, while Secure Syslog over TLS mandates TCP port 6514 to establish encrypted transport sessions.
Encryption and session reliability require connection-oriented TCP at Layer 4.
2
Identify the transport protocol and port number required for Network Time Protocol (NTP).
NTP operates exclusively over UDP port 123.
Time synchronization requires minimal latency overhead provided by connectionless UDP.
3
Synthesize the ACL requirements to combine both port definitions.
The firewall rule must permit TCP port 6514 for Secure Syslog and UDP port 123 for NTP.
Matching both service specifications ensures secure log collection and accurate time synchronization across subnets.

Key Concept

Port and transport layer protocol mappings for Secure Syslog (TCP 6514) and NTP (UDP 123)
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Topics

Common Ports and Protocols

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