When transitioning from Intrusion Detection System (IDS) mode to Intrusion Prevention System (IPS) mode, it’s critical to review and refine configurations to ensure legitimate traffic is not blocked. Here's the reasoning behind each option:

A. Disable traffic inspection and reboot before re-enabling traffic inspection with the new mode.

Incorrect:

Transitioning to IPS mode does not require a full reboot or disabling traffic inspection.

This step is unnecessary and could lead to downtime that impacts network operations.

B. Change the mode on one gateway at a time to establish a smoother transition period.

Incorrect:

While a phased approach might help in some large deployments, it does not directly address the potential for legitimate traffic to be blocked by IPS mode.

IPS operates in real-time, so misconfigured rules or policies need to be addressed before enabling IPS on any gateway.

C. Consider applying a stricter IPS policy to minimize issues during the transition period.

Incorrect:

A stricter IPS policy increases the likelihood of false positives, which could disrupt legitimate business-critical traffic.

During the transition, the focus should be on minimizing disruptions by fine-tuning policies, not making them stricter.

D. Check for legitimate traffic that has been flagged as a threat and allow list the associated rules.

Correct:

In IDS mode, the system only detects and logs suspicious traffic but does not block it. Reviewing these logs for false positives allows the organization to fine-tune policies and allow list legitimate traffic before transitioning to IPS mode.

By doing this, the company ensures that IPS mode will block actual threats while permitting legitimate traffic.

This is a proactive step to prevent unnecessary disruptions to normal operations when IPS mode is enabled.

References

HPE Aruba Gateway IDS/IPS Configuration Guide.

Best Practices for Transitioning from IDS to IPS Modes in Aruba Networks.

Aruba Network Threat Management Documentation.