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Difficulty: MediumNetworking Ports and Protocols

A network administrator is configuring inbound access control list (ACL) rules on a perimeter firewall. The corporate security policy specifies that external clients must be permitted to securely retrieve email using IMAPS and securely access internal web resources using HTTPS. Which of the following default TCP ports must be allowed through the firewall? (Select TWO.)

  1. TCP port 993Answer
  2. TCP port 443Answer
  3. C
    TCP port 143
  4. D
    TCP port 80

Answer

The administrator must permit TCP port 993 for secure IMAPS email traffic and TCP port 443 for encrypted HTTPS web traffic.
TCP port 993 is the standard default port for IMAPS, enabling encrypted email retrieval via TLS/SSL. TCP port 443 is the standard default port for HTTPS, enabling encrypted web traffic via TLS/SSL. Together, these two ports fulfill the organization's requirements for secure email and web connectivity.

Step-by-Step Solution

1
Identify the required secure protocol for email retrieval.
IMAPS (IMAP over TLS/SSL) operates on default TCP port 993.
Standard unencrypted IMAP uses port 143, whereas the secure variant IMAPS uses port 993.
2
Identify the required secure protocol for web traffic access.
HTTPS (HTTP over TLS/SSL) operates on default TCP port 443.
Standard unencrypted HTTP uses port 80, whereas the secure variant HTTPS uses port 443.
3
Select the default port numbers corresponding to the two secure protocols.
TCP port 993 and TCP port 443 must be permitted on the firewall.
Both selected ports enforce the required TLS/SSL encryption layer specified in the security policy.

Key Concept

Standard default port numbers for secure network transport layer protocols (IMAPS on port 993 and HTTPS on port 443).
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Topics

Networking Ports and Protocols

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