The requirement is that all traffic "must be encrypted at all times." This mandates a configuration that strictly enforces encryption and prevents unencrypted traffic flow. MACsec is a point-to-point Layer 2 encryption protocol, requiring configuration on both the on-premises device and the AWS Direct Connect endpoint.

First, the same MACsec secret key (CKN/CAK pair) must be configured on the company's on-premises router to match the key generated in AWS (Option A).

Second, on the AWS side, the CKN/CAK pair must be associated with the Direct Connect connection. To meet the strict encryption requirement, the MACsec mode must be set to mustencrypt. This mode ensures that the connection will be down if a secure MACsec session is not established, thereby preventing any unencrypted traffic. The logical operational sequence is to associate the key first and then update the encryption mode (Option D).

B: While the actions are correct, the order is less logical. Associating the key before enforcing a strict encryption mode is the standard procedure to prevent configuration-related link failures.

C: The shouldencrypt mode is incorrect because it allows unencrypted traffic if MACsec negotiation fails, which violates the requirement that traffic "must be encrypted at all times."

E: The shouldencrypt mode does not meet the strict requirement for mandatory encryption, as it permits the connection to pass unencrypted traffic if a secure session is not established.

1. AWS Direct Connect User Guide, "MACsec" section: This document outlines the configuration steps and encryption modes. It states, "To enable MACsec, you must do the following: ... 2. Associate the MACsec secret key with a connection. 3. Configure your on-premises device." This supports the actions in options A and D.

2. AWS Direct Connect User Guide, "MACsec" section, under "Encryption modes": The guide defines the modes: "mustencrypt – The connection is down if the MACsec session is not established. shouldencrypt – The connection is up even if the MACsec session is not established. Traffic will flow unencrypted." This confirms that mustencrypt is the only mode that satisfies the question's strict requirement.

3. AWS CLI Command Reference, directconnect, update-connection: The documentation for the update-connection command shows that encryptionMode is a parameter that can be set to mustencrypt or shouldencrypt. This is a separate action from associating the key using the associate-mac-sec-key command, supporting the sequence described in option D.