Explanation
Logging at session start should be used as a best practice while troubleshooting. Logging at session start allows the administrator to see the logs for sessions that are initiated but not completed, such as sessions that are dropped or blocked by the firewall. This can help the administrator to identify and resolve issues with network connectivity or firewall configuration. Logging at session start should not be used for normal operations because it generates more logs and consumes more resources on the firewall. Option A is incorrect because logging at session start should not be used on all Allow rules. Logging at session end is sufficient for Allow rules because it provides information about the completed sessions, such as bytes and packets transferred, application, user, and threat information. Option C is incorrect because logging at session start can be used independently of logging at session end. Logging at session start and logging at session end are not mutually exclusive options. Option D is incorrect because logging at session start should not be used only on Deny rules. Logging at session end is sufficient for Deny rules because it provides information about the denied sessions, such as source and destination IP addresses, ports, and protocol.