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Difficulty: MediumCommon Ports and Protocols

A network administrator is creating an Access Control List (ACL) rule on a core router to permit secure, encrypted email retrieval for clients connecting to an internal mail server using IMAPS. Which transport protocol and destination port pair must be explicitly permitted in the ACL configuration?

  1. TCP port 993Answer
  2. B
    UDP port 993
  3. C
    TCP port 143
  4. D
    TCP port 995

Answer

TCP port 993 must be permitted in the ACL rule.
IMAPS (Internet Message Access Protocol Secure) uses TCP port 993 by default to establish an encrypted TLS/SSL session for retrieving email messages from a server.

Step-by-Step Solution

1
Identify the requested network application protocol and requirement
The scenario specifies IMAPS (Internet Message Access Protocol Secure) for encrypted email retrieval.
Determining the exact service and security level dictates the appropriate protocol standard.
2
Determine the transport layer protocol required for email retrieval
Email retrieval requires reliable, connection-oriented delivery, which uses TCP rather than UDP.
TCP guarantees ordered delivery and packet acknowledgment necessary for message transfer.
3
Identify the default port number for IMAPS
Standard unencrypted IMAP uses TCP port 143, while IMAPS (implicit TLS/SSL) uses TCP port 993.
Port 993 is assigned by IANA specifically for IMAPS traffic.

Key Concept

Common Ports and Protocols (IMAPS over TCP 993)
Estimated Time:1m 0s
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Topics

Common Ports and Protocols

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